While complaining about Signature Abilities that don't match the flavor text might as well post others I find questionable from all other gens:
Skitty family & Normalize: Just why? It's not only a not-so-great Ability but has no lore connection whatsoever. Skitty likes to chase things (mainly its tail, running around until it gets dizzy) and is a popular cute pet though fussy on who it likes. Delcatty make no permanent nests, they eat and sleep wherever they please (having no set schedule for when it does aside being mostly active at night) and would just move to another location if bothered; they also don't like dirty places and will groom themselves clean. Heck, that doesn't really sound normal to me, they sound erratic. Looking at the Gen III Abilities think Hustle would have been good for them, or maybe Run Away.
Sableye & Stall: It hides in the dark, digs for gems with sharp claws, eats said gems which form on the surface of their skin and transformed their eyes, and people fear their gaze. First, there's many Abilities that match that, but since Stall was for some reason given to it in Gen IV we'll stick to Abilities that existed then: Intimidate, Pickup, Adaptability, Tinted Lens; and none of these are Signature. Second, what does Stall have anything to do with this? How does giving it an Ability that makes it move last no matter sound like a good idea. This is an Ability like Truant and Defeatist where you give it to a Pokemon so that you can give it very high stats to compensate, but Sableye wasn't even strong to begin with! Not to mention a generation later you gave it Prankster as a Hidden Ability, what's the point of it all?!
Drifloon family & Flare Boost: Okay, I get at least Driftblim is based on a hot air balloon which is normally lifted up into the air via hot air from a flame... but that's got nothing to do with the Pokemon themselves. Drifloon are either floating around seemingly aimlessly or are trying to drag a kid to the afterlife (and generally failing). Drifblim are carried around by the wind, sometimes letting people and Pokemon ride as they float through, and then they completely vanish at evening/dusk. No mention of fire or burning. Heck, Flare Boost powers up their Special Attack when normally you give a hot air balloon more fire to speed it up/make it ascend.
Galarin Stunfisk & Mimicry: Castform's entire concept centers around its Forecast Ability (and Weather Ball move), so why didn't the Terrain version of this Ability get the same treatment? No, instead they tossed it onto Galarian Stunfisk which honestly really needed another Signature Ability adapted to what it needed (like a Steel-type Aerilate cause the only physical Steel-type move it learns is Metal Claw; BTW they made Galarian Stunfisk a Physical attacker but then made the Terrain version of Weather Ball a Special Attack... GF WHAT ARE YOU THINKING?!).
Durant & Truant: Okay, I know not really a Signature Move (though as of right now it is since the Slakoth family aren't available in Sword & Shield yet, this happened to some Abilities and so Bulbapedia is now counting them as new Signature Abilities), but still why? And no, it's not for a pun as Durant and Truant sound nothing similar in Japanese. Durant are ants and they're all about working together to build complicated mazes & protecting the nest against Heatmor (and now Sandacobra which likes to eat their eggs). Nothing "lazy" (which is its Japanese name) about that, they're all busy bodies. The only ant which would be considered "lazy" is the queen and there's no female-only evolution which becomes an ant queen.
Fletchling family & Gale Wings: Now I'm not arguing why they get it, they fly pretty fast, I'm asking why no other Flying-type get it? And I know, that's not the point of this and you can say that for a whole batch of other Signature Abilities, but Gale Wings REALLY stands out to me as a notable example.
Stonjourner & Power Spot: Stonjourner's dex entries only talk about it mysteriously gathering up, standing around, and doing powerful kicks. And instead of having a kicking version of Iron Fist or some other existing Rock-related Ability like Solid Rock it instead has an Ability which powers up allies. Okay?
Duraludon & Stalwart: Duraludon is only said to be made out of a metal that's light & strong but rusts easily so hides in caves cause it dislikes rain. Now, I'm sure it's also a hardworker and handy to lug around metal beams around construction sites, but that really enough for it to be the only Pokemon with this move? Now it's Japanese name, Staunch, has the same definition BUT it also has the second definition of meaning something is strongly built so I guess that fits a little bit better as Duraludon can Gigantamax into a skyscraper resistant to earthquakes (that's what the dex says, we know that's not true). Still a bit of a stretch and a weak reason for it to be a Signature Ability. At least Corviknight's dex entry mentions its black luster feathers so that justifies it have Mirror Armor (though that wouldn't also hurt being spread around).
If it wasn't for the fairly indepth look at DP's various betas I'd wonder if they were intended to be ground type and located in a cut desert/arid location at some point. Even if you didn't want to put it in the post-game desert surely the route that connects with Hippopotas' cave would've worked or any of the million caves or something.
Wait, there's no desert in Sinnoh? Yeah, there's no desert in Sinnoh. Then where do you find Hippopotas? *Searches* MANIAC CAVE?! Weird. With a clearly desert-based hippo and those dex descriptions I wouldn't be surprised if there was a desert area originally planned but maybe dropped early on cause they already had a big desert location in Hoenn and didn't want to repeat leaving both Pokemon intended for the location, Hippopotas and Skorupi, stranded. Hippopotas they shoved in a cave while Skorupi they put it in another location you find scorpions... completely forgetting about the dex entries.
Though, to be fair, it does only mention sand and where else do you find sand aside from the desert? Around water sources like beaches and rivers. Most recent dex entries of Skorupi notably no longer include it "living in arid places" part. Meanwhile Drapion has more recently also been put into mountainous locations, notably Galar Route 8 (where there's also Hippowdown).