Added an edit to my original comment. I don’t think it even has to be “indistinguishable”, or even AI. I imagine that even “tributes”, or even just posting SFW pics and just making sexual comments about them would get smacked down hard by the law. And remember that whole thing with the mother who accused a doll company of basing their product on her child?
Now, it was found that this woman made the whole thing up (FL Woman LIED about Child Sex Doll using her Daughter's Likeness), but let’s philosophize and assume a situation like this actually occured. Could the dollmaker be charged with producing sexual content of a minor? Let’s think another scenario, where a person made a 3D model instead of a doll. Would that be charged as CSAM?
The grayest area I’ve seen is ripping a mo-capped model from a video game and manipulating it for sexual purposes (like Sarah Miller from The Last of Us, mo-capped by then-12yo Hana Hayes), or clearly basing your drawing on the likeness of an actual child (like Emma Watson as Hermione or Millie Bobbie Brown as Eleven).
Sometimes, the line gets so blurred it’s hard to keep track. Obviously, the one line most do not cross is directly engaging with unambiguous CSAM or actually interacting sexually with a minor. Other than that, it’s kinda all over the place.