How do you know it's not bodies of willing adult pornographic actors that merely appear child-like?

Why would you swap faces when you already had the pictures, if not to hide the adult facial features?

By that argument, deep fake porn shouldn’t exist at all. But it does, so clearly that’s not the way these people see the world. Some faces are simply “better” than others, at least in so far as those with perverted pornographic desires are concerned.

Regardless, child faces in adult bodies is in fact still illegal, see this detailed court report for more info: https://casetext.com/case/united-states-v-smelko-2

To amend my prior comment, the law says that the face actors in fact are harmed as well, reputationally. Fair enough; I’m not here to play “defend the pedo”.

It exists because face is what gets visibly aged on people even if the body isn't easily distinguishable from children. Why is it called "child sexual abuse material" if no child was abused in its creation?

Ad reputational damage - OK, I agree if they distribute it, that's fair. But if they don't distribute and the police finds it only after they take their hard drives?