Well i've recently updated to the latest version, and previously had the same problem, only when touching anything it WOULD audibly continue playing. So for that reason i don't think u'r diagnosis of the problem as being similar as WMP is corrent. I think microsoft was just too lazy to make WMP work with hibernate so they make it just stop playback when it see's a hibernate event. it's a different thing i'd say.
I don't think there is any fix for it, nor should there be, thats what new versions are for. So if anybody has this problem they really should just get the latest version