I found this description in the One-Shots forum (I'm sure I've seen it elsewhere, though)
Extreme - A category for gore, guro, vore, bestiality, and other elements that might gross out even those who enjoy bondage and/or non-con.
(Emphasis mine) So, yes - if you've got body parts flying around on a regular basis, and think it might put someone off their lunch, you might be best off tossing it in Extreme, even if there's no sex involved.
(That just sounded wrong, didn't it?)