Late to the discussion, but I think the thing to note with Leon is that his title and how he was portrayed as "the strongest Champion ever" specifically was made with respect to Galar's culture, especially in its League. In no situation should a character being described as "the strongest Champion ever" with respect to their region ever be taken to the literal wording, because it's impossible for anyone to literally be the most powerful Trainer in the world.
Galar's Pokemon League has a massive rooting in sports culture and is treated as public entertainment like how IRL you have sports being broadcasted as live entertainment on TV and in stadiums and whatnot. The Gym Challenge is held yearly and is treated as a big sporting event. The Gyms are massive stadiums with audiences and it's implied that Gym Battles are broadcasted on television as well. Every year they also have a big Champion Cup tournament in Wyndon for Gym Challengers to compete to earn the right to face the reigning Champion, who in SwSh itself is Leon. Which, mind you, also is a big public event. Battles in the Gym Challenge are basically a big sport, and fans across all of Galar treat it as such.
Leon being portrayed in-game as "the greatest Champion ever" is basically propaganda that comes with this kind of entertainment business. Yes, at his core, he is a guy who went on a journey when he was 10, became Champion, and has had an undefeated streak ever since, he's the real deal and a mirror of the player character. But him being glorified is basically tied to the Galar League being sports entertainment, and a title to prop him up and make him look "awesome" to the general public. Basically, a way to give Leon celebrity status. You know how in sports; the best and most skilled players often get propped up and given fancy titles and are made famous and end up with lots of fans? Yeah, that's Leon in a nutshell. He's propped up as a celebrity because battling is a sport in Galar, and he's basically famous and has a massive fanbase because of that and how he's the "top player" amongst Galar's battlers. You can see how he has a cape with so many company logos on it and how he goes around putting on a show for people, and how his battles are always portrayed as a big spectacle and how he puts on a public front for everyone to align with his title as the "strongest, undefeated Champion".
A lot of Leon's character in SwSh delves into how he feels about the weight of carrying the burden of that title. That he's never lost, that he has a reputation as a celebrity that hinges on that and how strong he is, and how living up to those expectations imposed by other people has really caused a great deal of stress on him and has also given him worry that he's reached his full potential. Most of his depictions even outside of the games (like the anime) also play on this. He's propped up as a great unbeatable Champion for purposes that tie with respect to the Galar League being rooted in sports culture, which helps make defeating him feel more awesome and a great feat, yes. But it also concludes Leon's character arc in that he learns he can lose again, that he can still get stronger, and that yes, there are still people who are even stronger than him. And it relieves him of those expectations, which is why he's happier when he loses his Champion position. Because he's free of having to live up to the expectations of others as a celebrity, and he becomes League Chairman afterwards where he lives not for a public image to maintain, but for his own dreams and ambitions of helping Galar's Trainers grow even stronger together. That's really what his character was all about. His title and shilling were tied to the culture that Galar had, and his character revolved around how he dealt with and felt about his public persona vs what he really wanted to live for.
I went on a tangent about Leon, but point being, this isn't really comparable to Geeta from my understanding. I haven't played SV yet, but Paldea's Pokemon League from what little I've heard and seen seems to have a fundamentally different approach from Galar. In Paldea, the League seems to be more of a professional business as opposed to a big sports entertainment. Instead of being like publicly broadcasted sports, the Gym Challenge and League. The Gyms are more like job interviews or business opportunities as opposed to a big event for sports purposes. You know how a professional business/company has a general hierarchy and employees are in various positions of power? Yeah, that seems to be how the Paldea League is organized. Like a big company that is a business, and Gym Leaders and the E4 and whatnot are employees of the company. And the academy in Paldea seems to be more akin to a college than K-12 school, which also works here as the Gym Challenge taking in people from the academy as potential "hires" for positions amongst Paldea's Champions.
Geeta being portrayed as the "strongest Champion in Paldea" ties into that sort of vibe with the fact that she's specifically also the chairwoman of the League here. In that since the Paldea League is more like a professional business, she's a figure of authority in that she's the owner of said business, the head of the company, the CEO, the top person in the business hierarchy. And her being the strongest Trainer in the Paldea League is enforcing that. Enforcing her as a person in a position of authority, at the top of the business. She runs the business, and she's the strongest battler amongst all the members of the "company" hence why she is at the top of the hierarchy as the one who runs and oversees everything that happens in the business. And also why she's basically the final boss/test for Gym Challengers who go through the League to earn the right to the title of Champion. Unlike Galar where there is one reigning Champion and Leon is ultimately dethroned and a new person becomes the big star of the show, in this case you're basically climbing to the top of the tower of a business conglomerate, because in Paldea the title of Champion is an honorary title you hold permanently a la Top Coordinator in the anime. And you win that title by proving yourself worthy to the head of the business, the chairwoman, Geeta, who is the one who runs the Paldea League and reinforces it by being the best Trainer amongst the lot. You defeat her, you've earned the right to the title of Champion and a high position in the hierarchy as a member of the Champion Rank in the Paldea League. So in that sense, she's more of a "she's the CEO of the business, you win the position you're aiming for in this business by proving yourself worthy to said CEO".
I rambled a lot here, but TL;DR There's really not an issue with "power creep" when it comes to portraying a Champion as the "strongest Champion ever" when you consider the different contexts in SwSh and SV, and the title isn't something you can take literally and more something you have to think about with respect to the different contexts. Galar has its League deeply rooted in sports entertainment culture, the whole thing is a big public entertainment event that has big stadiums with audiences and is broadcasted across Galar, Gym Challengers and Gym Leaders are all "players" of the sport and Leon is basically a celebrity akin to iconic sports players who is propped up for his talent and then gains a massive fanbase and celebrity status surrounding his "undefeated streak" to prop him up as a public figure and give him a glorified public image. Paldea treats its League more like a business, and Geeta being propped up as the "strongest Trainer of them all" is tied to her being the chairwoman in this case in that it enforces her authority and power as the head and owner of the League, the person who runs and oversees the business, and her position isn't to be a celebrity like Leon, but rather as someone who's "in charge", so Gym Challengers aiming for the position of Champion Rank in the League have to prove their worth by defeating her, because she's the strongest Trainer in the business, ie the person at the top of the hierarchy, and with how Champion title is treated in Paldea it's effectively you earn the position amongst others by proving yourself to the chairwoman/CEO of the business that you are worthy of the position. It's not an issue of who's stronger, Geeta doesn't need to necessarily be "stronger" than Leon, and neither of them being described as the strongest in their respective regions should be taken at the literal sense, but rather with respect to the League cultures in Galar and Paldea and how their positions in said cultures are being enforced.