The CW'd version gets a blurred thumbnail on my profile but only appears as the CW line on my home feed.
I was hoping it'd do the former everywhere, I'm considering posting my furry kink art on Mastodon and I prefer the blurred preview for that, it's more eyecatching and obvious at a glance that the hidden thing is art and not just a passing post
I could just mark the image as sensitive, but then I'd have to make sure the text of the post isn't sensitive in and of itself...