Actually they already have the loophole. You can use Visa/MC for anything legal, BUT they want a 20% fee (as opposed to 2-3%) for adult content/products due to being 'high risk'. Itch.io and Steam and being told they would have to pay that higher discount rate for all transactions.
It's not just NSFW content, they also do the same for firearms related transactions. They want more $$$ is really what it comes down to. They claim it is due to being high risk, reality is they know no one is coming to defend pornographic material creators. Now you have 'evangalists' who are...
Instead of the abstract, I would suggest reading You must be registered for see element. (I know, summaries are just easier). What do they define as CSAM? Does it include links to things like screenshots of games like 'Proud Parent' despite containing no real people? Who was the 'third party'...
Think of the datasets as the knowledge acquired by observing, not just AI learns this way as humans do as well. Humans literally go to school, read books, even watch movies to learn from others and expand our own dataset. Unless somehow everyone agrees to stop (didn't work for nukes either) it...
The "questionable" content was no worse than items you find on an average year of browsing the internet, it was really blown out of proportion by media and politicians to garner attention. They claimed that if it can generate images of things like rape it MUST contain them in it's data set...