I don't know if this really fits the thread but it kinda pisses me off that in Gen 9 they removed Mystical Fire from Sylveon's learnset. That move was so cool for it, and arguably a bit iconic of a set- it's literally in Pokemon Unite:
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Which often takes some inspiration from competitive sets/moves.
I don't really get the way they handled this. It's not even like they took it off every non-Fire, Gardevoir Mismagius Flutter Mane Enamorus Hatterene all still learn it.
And if you think Sylveon isn't witchy enough, like, why doesn't Espeon get it? Espeon has literally had official promotional artwork and plushies as a Mismagius-Witch:
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speaking of which if anyone has a free kidney LMK I want this in my life
I think the reason it lost it is pretty simple: it's not a TM anymore.
Flareon
also lost the move for the same reason.
& unlike Gardevoir (learns it by Egg Move & level 1), Hatterene (egg move), & Enamorus, they passed on giving Sylveon the [pretty good] fire move by default because they want the Eevees to stick to their type lanes when it comes to level up moves. & eevee doesn't get to have fun "break the typing" egg moves.
Honestly even with the fairy typing backing it up I'm surprised they gave Sylveon the move to begin with. Especially when as you point out Espeon doesn't get to have it, so I dunno not even a case of matching how so many of the fairies, psychics, fires & ghosts learn it.
Now that said double checking all these movesets I do have my
own questions like:
-Why does Eevee get to have Trailblaze & Alluring Voice? This gives all the eevees access to those moves when both seem like things that should only be given to Leafeon & Sylveon. Bite's kind of in the same boat but that's a long-standing level up move so you kind of give it a pass; but these two were brand new TMs and stick out a lot in the learnset. (Now granted Alluring Voice is a DLC TM but it does feel like...if you're going to hand out the 80 BP fairy move to everyone why NOT just let it learn Mystical Fire as an egg move)
-Flareon & Glaceon don't "learn" Bite at Level 1 like the other eeveelutions do, instead learning it at 25 like Eeevee does. Kind of weird.
-Likewise, Espeon & Sylveon learn Swift at Eevee's level instead of level 1.
--Which is double weird because the Swift level up slot is used for status/weird moves like Haze, Smog, Thunder Wave and so on. Even with dexit and such there's still plenty of Psychic & Fairy moves that would fit that kind of archetype
AND WHILE I'M HERE when GameFreak were putting together Mismagius' set for L:A did they forget it not only had Mystical Fire since ORAS, but was one of only 3 Pokemon to learn the move before the SWSH TM. It doesn't learn it at all in L:A but Drifloon's line does...and then Drifloon lost it immediately in the transition to SV despite it being a level up move so you can't even lean on the tutor aspect.