Why do you care if an 18+ year old who looks youthful does NSFW stuff? Take an extreme example, what if Hasbulla did nudes? He is 21 but looks extremely young. I can't see how telling him he isn't allowed to make nude content because of his appearance is anything other than ableist and body shaming. You don't have to like the content or even like the people who would look at it to think the content is acceptable.
If everyone is a consenting adult then everything is fine.
I'm not subscribed to that community. It's not my thing. I'm not into Loli either. Frankly, I do see a problem with Loli. I guess to me it is because the Loli "excuse" of "she's actually 3000 years old but just looks like a child" but then they proceed to portray them exactly as someone would portray a child. They (generally, I'm sure someone has counter examples) don't portray them as some wizened elderly woman in a child's body. That's why Loli generally feels disgusting to me.
Age verification is the correct thing to do. In the broader internet where things are less strict I'm sure you can find actual underage actors (who are possibly even being trafficked) where it could be avoided with proper age verification. Frankly I think that's just a super important thing (even apart from this specific discussion). An assumption I'm making (and I guess everyone is) is that the admins' age verification is adequate. So, assuming it is, I don't see a problem with allowing creators who appear young to make NSFW content of themselves. If it's not adequate then there's a much more important discussion that needs to be had. Based on some of the sticky posts over the past few weeks it seems like they're serious about it.
To your point, a lot of content makes my skin crawl. I just ignore it. If there's any I think is actually illegal I'd report it. Maybe I haven't seen the specific ones you're talking about so maybe that's why I don't feel the same way. I briefly went to the community when I heard about this and just now to see what the fuss was and it just seemed like legal but youthful looking people. Or just folks in their mid twenties just trying to look cute or wholesome. I didn't see anything that makes me feel the need to report anything as CSAM. That's just me. I believe you should report content you think is CSAM, I'm not trying to say you shouldn't.
I know I said it before but I really do view this whole thing similar to folks who may not understand forms of kink are consensual. It's not a one-to-one thing, but it is similar. Seeing a consensual rape-play session may make people question what the fuck is happening and may make their skin crawl. But if everyone is consenting then it's fine. I understand why people would have a hard time accepting that (especially if they themselves have been abused).