This is rather annoying, because adding part of (P361) is fine for most music release items because they're not formalized into the MusicBrainz-style entity structure; but for the 100 or so items which are split up I have to revert the same edits from Harvest Templates every time. I don't really think there's a good solution which doesn't involve breaking something for either group of items.
@Moebeus: do you think there's a constraint violation which could be added temporarily to part of (P361) to prevent this?