Yeah, seems like anyone clicking through is playing with fire. If the description is correct, posting the link is highly irresponsible. (It seems like the right thing to do would be to serve the content from a server the OP controls themselves.)
Maybe I'm an idiot but my curiosity got the best of me and I clicked the link. The photos just look like abstract modern art, although their perceptual hash may match that of known CSAM, I doubt that anyone who clicked the link will get into legal trouble even if Google flags that folder by detecting a perceptual hash match, as they will likely use real people to verify before taking legal action.
Google has been recently focused on cultivating the image that they care about user privacy. The last thing they want to do is call the cops on a bunch of HN users for looking at some abstract swirly pics.
I think the concern here isn’t legal trouble but getting banned by some automated system.
I’ve heard from googlers that once an account is nuked for suspected child abuse no one will ever want to touch it to find out whether the ban was legitimate.