I never believed there was such thing as a "level reset" in the anime. It's super jarring when "levels" are put into the anime instead of just using experience as a general thing, hated it before when OS pulled it and I still do.
Pikachu goes back to fighting like normal a while after he was sapped of his electric powers doesn't he? As far as I'm concerned, a level reset wouldn't mean he goes back to being strong again the next episode or anything, the dude would probably be using weak things like Thundershock again and whatnot if this so called "level reset" was a thing and would work his way back up. He just lost his powers for a bit and had to recover. I'm sorry but I just hate that term being used for this case. That Snivy knew Leaf Storm ffs, that is NOT a "Level 5" thing. VINE WHIP is. And again, the levels thing, just because its a Snivy at the start of the anime doesn't mean it's automatically "Level 5", it's just a fricking Snivy. We had a Bulbasaur in the very first series who literally refused to evolve, I don't see people calling him "Level 5" or anything.
I'm not trying to sound salty, but it kinda shows how flawed the "Levels" being put in the anime is. Experience sure, that can be used as an in-general thing, but the "Level 5 Snivy" and "Level Reset Pikachu" thing I never liked seeing in discussions of the BW anime, because the anime doesn't work off of that bit of game logic, and when it tries to it's super duper rare it does to where it's forgetable.