>>27031151Pokemon was a game first, the sizing you see in the anime is only seemingly large because the world they live in exists within the game.
So Ash is technically a Pocket human.
All of these monsters and their universe fit inside your pocket. Pokemon aren't mostly small at all in their universe, they aren't made for your pocket in that universe unless captured in a pokeball. Which is kind of funny, we put small creatures in a game that fit in our pocket, then in that game universe they put the creatures in a smaller item that can fit in their pockets.