But what if you distributed a model from the game and I drew a moustache on it? There, it's no longer Square's content
Then all but the mustache is their data. 100% fan-made models are already nebulous legal territory but generally ignored (at worst they would constitute trademark infringement, not copyright infringement, and companies really don't care), but the actual original data is totally, entirely copyrighted.
If you want to rip the model yourself and inject it into your own copy of the game, that's fine though.