Yeah, point taken, it IS a bit tenuous.  But I do think it's relevant.  It's a hard one to call because it's a fairly unusual album.  But it isn't a side project or a different band - Dani and Pybus are basically on there representing Cradle of Filth as part of the Roadrunner stable, so for that reason I vote it stays where it is (although there's no reason it shouldn't go on their personal pages in the way you suggested).  I guess it COULD go into Trivia, but then people would probably question why it wasn't with the rest of the albums...