Their criteria was “John Oliver looking sexy,” but no NSFW was stated, no. In fact, they clarified that John Oliver always looks sexy, so all pics of him were acceptable.

I just read the article on this yesterday. It was /awww, /pics, and /gifs as the first to do this (with I think pics starting it)

Very amusingly, it was first stated that “only sexy pictures of John Oliver would be allowed”, but then it was changed to, “all pictures of John Oliver are allowed, because every picture of John Oliver is sexy”

Edit: I see someone else already mentioned the “all pictures of John Oliver are sexy” bit. Sorry, I just missed it somehow.
As a further edit, here was the original article