I believe in it, however my view of it is that the person who's shifting is not staying stuck in one "shift", but is either constantly moving towards a full shift, or back to being human. I guess, not like shifting a wolf's tail and ears, keeping them on like that and leaving the rest of you human, but every part of you shifting at the same rate gradually until you fail to complete the shift (for whatever reason), and go back slowly into a human form. I consider that to be a partial shift, though I'm aware that most people seem to mean more like shifting paws and tails while remaining human, and keeping the parts on without them going one way or the other.