I am not sure if CSAM is the only reason for this group - notice they specifically listed MILF/DILF, that doesn't involve or imply CSAM in any way.
One needs education to explain that, for example, hentai manga has little to do with realism, that character drawing styles have a long history that is only partially intertwined with lolicon wave started in the early 1980s (and that they even cross-pollinated with female-oriented manga along the way), or that the strict indecency ban (again, thanks to US) had created it in the first place (so little girls were actually used to portray proverbial 900 year old vampiresses because you could not draw those vampiresses that way).
Then we can see that any kind of image, even highly realistic, even photographs, is a deliberate set of choices made by the author, not a 1:1 copy of of “reality”. Then we can switch to the viewer side, and study how the contents of people's head define what they see, and how they react.
Here's a party trick. Japanese entertainment industry still produces a significant amount of media with young women in bikini. Weekly Young Magazine (one of the biggest manga periodicals) keeps placing idols on the front cover to this day. Ask someone about it, and listen to the expected comments about “questionable”, “seedy”, and “exploitative” nature of those (which are obviously true to a large extent). Then compare that to Western media products, global pop stars and such, and enjoy the excuses about it being completely different, “suitable for the whole family”, and “playing by the rules”.
Also we're not arguing the language here or its adherence to the specific reality, but the blunt tool the laws are.
Putting other countries laws aside, I believe that digitally manipulating the image of the real child in that way results in the production of the actual CSAM and as such is a federal crime.
And back to my previous comment - actual children are involved, so the abuse actually happens. If you doubt it, feel free to read up about women who experienced their own AI-manipulated pictures to make them appear naked - I don't think you deny the actual harm here.
In terms of generation (harming pixels), I think the idea of the lawmakers is to criminalise similar ones as well ("indistinguishable from a real child") to offer some protections to real children.
There are orders of magnitude more CSAM on other platforms, such as Facebook. As explained elsewhere in the comments, Pornhub was targeted by evangelical, anti-pornography groups which weaponized claims of CSAM against Pornhub for their own political purposes, despite the fact that Pornhub had vanishingly few instances even compared to other pornography platforms, let alone non-pornography platforms (like Facebook).
