minimize (the move)

i'm kind of confused as to what this move is attributed to..
like... i get how some pokemon get stomp (they have hooves), horn attack (horns), bite (teeth)... but i don't get why those particular pokemon that have minimize have it as a move
like chansey, clefairy, staryu.. etc

I think its just a special power that a Pokemon can unleash, like Double Team, or Leer.

Is it even possible for Chansey to minimize

It's just a shrinking in size to increase evasiveness.

True, it's odd how Chansey can make itself smaller, but that's just something unique about it.

okay.... i looked up all the pokemon who can learn minimize... and they include grimer, muk (they're goops so yeah they can shrink), drifbloom and the other dude (they can deflate since their balloons), quilfish (they can get bigger and then deflate), but i don't get clefairy, clefable and chansey.. or staryu and starmie.. <_<
what's weird is that the jigglypuff family can't learn minimize, and they're literally balloon pokemon