This will also make the Nacrene Gym also being a Tutorial Gym make more sense as it'll teach you that, while the first Gym gave you a partner with the Type Advantage, Nacrene Gym you're going to have to catch yourself a Fighting-type Pokemon (and maybe then have a gift Roggenrola or maybe a Dwebble so that you have a defensive option you normally wouldn't have access to this early on).
I wouldn't really call Lenora a "tutorial" in the vein that Cilan, Chili, and Cress are. If anything Lenora is more like your actual typical "First Gym Leader" that you would typically meet like Brock, Falkner, Roark, Cheren, Viola, Katy, etc., in the sense that she's BW1's actual "first boss fight" like Brock/Roxanne/Roark, Falkner, or Viola/Katy are. She uses a common "early-game" type, Normal, which is in my eyes one of the four common "early-game" types: Normal, Bug, Rock, and Flying. In that sense she's actually closer to your traditional first Gym Leader after Striaton is basically a "mandatory tutorial".
Especially when you consider the general way the game is structured around the point you reach her. After Striaton, the pool of available options you have at your disposal widens up to be as wide as the pool of options you would usually get before the first Gym in your typical Pokemon game. And like how your options are usually a mix of advantaged and disadvantaged against the likes of Rock, Bug, and Flying, and a new player would have to figure out the best advantages (Rock, Bug, and Flying have intuitive match-ups against early game mons usually), in this case it's a matter of whether your options are strong enough in a vacuum to win.
Normal is basically the "baseline" type which is why it's a common early game type and effective as a "first boss": it's not really weak to anything but it also does not resist anything either. In that sense it's largely neutral. In return, it's also largely unresisted but doesn't hit anything super effectively. And while it's a bit different from Bug and Rock in that in those cases, one/two starters are advantaged while one is disadvantaged from a type matchup standpoint, in this case none of the starters have any type advantage or disadvantage against Lenora...in a vacuum that is.
That said, with the Unova starters they also actively went out of their way to give one of the starters an advantage against Lenora, in this case Tepig, who by the point you reach Lenora should have already evolved once into Pignite, who is part Fighting type and learns Arm Thrust upon evolving. This means players who chose Tepig basically have a free advantage with their own starter being a Fighting-type and thus being able to hit Lenora's Pokemon super effectively, basically making it the "starter who has the advantage" like Grass/Water starters against Brock, Roxanne, Roark and Fire starters against Viola, Katy, and Milo. That said, Servine and Dewott, who also should've evolved once by this point, are by no means ineffective against Lenora, and from a raw stat and power standpoint your starter should be the strongest Pokemon you have in your arsenal at this point, and despite not being able to hit Lenora's Herdier and Watchog super effectively in a vacuum, Servine and Dewott are still by all means strong enough to hold their own against Lenora.
With Lenora, the pool of options you'd have at this point are your evolved starter, Lillipup/Herdier, Patrat, Purrloin, monkey, Munna, Pidove, Blitzle, Roggenrola, Woobat, Drilbur, Audino, Timburr, Tympole, Throh, and Sawk. Note that as I said, this is a similar magnitude of available options you would usually have by the first Gym in most traditional Pokemon games in other regions (and BW2). And while Throh and Sawk are the absolute strongest options you have against Lenora and basically guarantee a win against her, you are not railroaded into using them nor are you necessarily obligated to use them to get the win. Many of your options are shaky because of a power gap between them and Herdier+Watchog, but your starter can still reasonably do well (you are basically set to win if you have Pignite), you can go for Timburr or Sawk/Throh to get the offensive advantage, or alternatively you can go for the defensive route with Roggenrola, who can use its high physical Defense and Normal resistance to endure hits from Watchog and Herdier defensively (and you can teach it Rock Smash to hit them super effectively too!). An NPC also give you a TM for Rock Smash nearby to teach to your other Pokemon as an alternative.
Lenora's Watchog is really more of an actual "first boss" Pokemon like Brock's Onix, Roark's Cranidos, Viola's Vivillon, etc. A Pokemon who's particularly strong for that point and can easily take down/wall the mons you will have at your disposal at that point but has a few loopholes that can be taken advantage of and it's on you, the player, to figure out how to beat it. And naturally, there will be some options that are more powerful/effective against Watchog, but it's not so unstoppable as to force you to use a specific option to win. You have multiple ways to win: brute force with your evolved starter, wall with Roggenrola, hit super effectively with Timburr/Sawk/Throh, or a combination of all of them. But ultimately it's on you to figure out a winning strategy: Lenora presents to you an actually tough fight, but the player has to figure out how to win on their own.
I ranted quite a bit here, but this ties into the recent discussion about the monkeys and Striaton Gym and how that whole thing is designed with respect to your available options.
Striaton is pretty much not really designed to be a boss fight nor intended to be actually difficult: it is straight up an explicit tutorial which is why the game railroads you into using the monkey for it. You have your starter (disadvantage), Patrat/Lillipup (neutral), and the monkey (advantage), and a new player in a vacuum hypothetically speaking will have all three: Patrat or Lillipup being their first catch that the game basically encouraged them to capture on Route 1. It's an explicit tutorial on how types can interact, and the railroading is designed in such a way that from a new player's perspective, it explicitly communicates two concepts: the concept of type advantage and disadvantage, and the message that you will need teammates of a variety of types to cover for each others' weaknesses to succeed.
Nacrene Gym and Lenora on the other hand function more as the actual "first boss" that most of the first Gyms do: Lenora is a genuine threat and a formidable/challenging opponent and at this point all of your usual early game options are available and obtainable, but only a select few will give you the advantage to secure an easier win: that said, it's not totally undoable to use alternative strategies to achieve victory. And your starter, no matter who you choose, can be your strongest weapon against them, even if one of them is strictly more advantaged than the other two (Pignite).
BW1's adventure and game is structured in an unusual way, so this is worth highlighting in regards to this discussion. That said, BW2's adventure is more like a traditional Pokemon adventure in other mainline games and plays a Normal-type Gym Leader as the "first boss" more straight with Cheren being
the first Gym Leader and being a Normal specialist while not having such an explicit tutorial like Striaton in BW1.