I imagine the same way they do for actual photographs in which they haven’t identified the victim, which I’d guess is a pretty big percentage. Stuff like this is never cut-and-dried, but the law deals with ambiguous situations all the time. The test for what even constitutes pornography compared to, say, medical images involving genitals is a good example.
I mean sure... but that's because there's an actual person photographed there. What happens when you get into "does (s)he look 17 or 18 in this photo?" and no way to prove anything, since the person does not exist?
