Say a Fanfiction writer wanted to have the Pokemon in their story able to use more than four moves at any given time in order to make the pokemon battles in the story more entertainiing.

What would be yer response?

7511802
A lot of people don't follow that rule in the first place.

7511812
Oh so I'm not the only one who thinks it's a little nonsensical.

I mean I can understand it in the games. But the Show really has no reason other than to follow the games.

I think it's totally understandable. The limitations exists in the games because, well, it's a game...

But the anime already opened exceptions a few times, like Ash's Snorlax using six different moves in one of his battles. I don't see why that would be a problem at all.

I'm personally against having more than four moves, if only for balance and fairness's sake. Plus, the anime's inconsistency with moves and rules were always nonsensical.

My personal headcanon is that four moves is a legal thing - your Pokemon doesn't "forget" moves to make room for new ones, but rather updates the list of the moves they're allowed to be using for official battles or tournaments. So they still know all the early-game stuff, they just aren't using them. Move Tutors then are officially licensed roster changers (with some neat moves only they can teach as perks to visit them for burgeoning Trainers).

7511813
It was instituted in the manga for at least one arc too - but that was specifically to showcase game-like strategies, I think.