They never give you a specific reason, but I would guess if pressed they would use the obscenity excuse. People slip forbidden things into clips all the time (especially on C4S), but if you have your own content site you risk having it shut down if you don't obey the rules. My guess is once it's set up, they don't look at it again unless someone complains.

On the Kink.com documentary the owner talks about this. His processor had contacted them saying any reference to "tentacles" was not allowed. Everyone had a good laugh over that.