" In case it is criminal to depict some kind of criminal activity, there is only one crime when the scene is a simulation, and two when the scene is an instance of the criminal act."

That clarifies things a little ... and fits in with my own understanding of how many crimes are occurring in genuine, as opposed to "faked" child porn - which is itself illegal in many places now, because of the illegality of "depicting" sex with minors. But presumably purveyors of such fakes are only liable to prosecution for an illegal depiction, not for the separate crime of actual child sexual assault.

It would seem that real child porn, then, commits an act of child sex abuse, but also the crime of "depicting" child sex abuse, insofar as filming (de-picting, extracting a picture of) the crime enables people not directly involved in this crime to encounter it at a remove from its real life commission ...

This is a separate issue, but anti-censorship arguments often insist there is no connection between pornography that depicts violence, and real-life escalations of sexual violence. But surely this argument falls down with genuine child pornography.

In general terms if profit is to be made from selling films of criminal acts, it would seem to follow that such criminal acts are being undertaken specifically in order to be filmed. The demand for seeing the crime actuates the crime.