Pokémon X and Pokémon Y

It's not illogical.

Mewtwo is a clone of Mew. It makes sense that as Mewtwo "awakens" and becomes more powerful, it becomes more like the original pokemon that created it. Mewtwo is transitioning from a man-made pokemon into it's own species, and therefore looks more like a pokemon and less like a human.

I see.
So Mewtwo get's smaller, because when he gets stronger, he becomes more like the original pokemon that created it.
I just find getting smaller when you get stronger an illogical concept, because like @Lozmaster pointed out; it almost never applies to pokemon...
I also don't get what, Mewtwo transitioning from a man-made pokemon into it's own species, and therefore looking more like a pokemon and less like a human, has to do with me using buu and mewtwo as an example to point out that I find getting smaller when you get stronger is an illogical concept...

Just sayin'

Oh, my bad. I forget sometimes that the world where it is considered an advantage to be using a tiny electric mouse against a fully grown whale is completely logical.

Oh my bad for having an opinion. I forget sometimes that that's not allowed on the internet.

I only find it illogical, because like u said; it almost never applies to pokemon.