That's not the gotcha that you think it is because everyone else out there reading this realizes that these things are able to combine things together to make a previously non-existent thing. The same technology that has clothing being put onto people that never wore them is able to mash together the concept of children and naked adults. I doubt a red panda piloting a jet exists in the dataset directly, yet it is able to generate an image of one because those separate concepts exist in the training data. So it's gross and squicks me to hell to think too much about it, but no, it doesn't actually need to be fed CSAM in order to generate CSAM.