well they just simply never made a naked model....the clothes are the body if there is none there is no bodyNow, this might be a crazy theory, but hear me out on it: I think I know why that when the shirt is gone, that part of the body is invisible. I don't know, but I guess in the event that people who hack with tools like Cyber Gadget, they'd have a way to censor? Again, just a hypothesis. It's either that or Game Freak didn't make anything under the shirt.