It's certainly technically possible. I suspect these AI models just aren't good at it. So the pedophiles need to train them on actual images.

I can imagine for example AI doesn't know what puberty is since it has in fact not seen a lot of naked children. It would try to infer from all the internet porn it's seen, and draw any female with big breasts, disregarding age. And that's not how children actually look.

I haven't tried, since it's illegal where I live. But that's my suspicion why pedophiles bother with training models.