Of course, an actual lawyer could probably explain why this would be a bad idea, but at least I as a non-lawyer don't see where the problem lies (aside from the fact that the company wouldn't want their stuff to be used to create CSAM, which is fair).
But these AI systems do not just generate CSAM by happenstance or the user tricking them into doing it. These systems have their training data obtained by scraping everything off the internet. There is a lot of CSAM (and whatever you will call text/literature describing such things) on the internet, and so, in the training data.
OpenAI had some of their Kenyan data tagging partners quit the contract because they had to tag which images and text were CSAM. (With none of the already-insufficient mental health resources afforded to social media moderation staff)
To be graphic as possible, if your commercial AI application generates childporn you will be fistfucked by the long arm of the law in at least the US, Canada, and Japan. While chasing individuals is more difficult for law enforcement a big juicy target like Google could rack up billions in fines.
Put frankly, the law gives zero fucks about that. Looks like child = jail is the law in many countries in which Google operates.