I'd agree with that, well, certain edgy topics could do with an age restriction of 21+ given that the brain is not fully developed until at least around that time. They don't give people that option, though, they may do in the future, requiring legal forms of ID. But right now, ChatGPT has too broad of a brush in what they allow and what they don't.
Of course children should not have access to NSFW content. However as far as adult content goes, censorship does not always keep people safe, in fact a lot of the time it does the opposite, as it keeps people ignorant of what is dangerous and what is not, they seek out less safe ways of doing things under the radar. And if this is the future of web guidelines, I worry for people, because they are not being treated with the dignity and autonomy they deserve.