I find this quite funny considering they are doing a world-wide unveiling of one of their new Hangout features with such a profile: https://plus.google.com/u/0/109351399938437494273/posts
Regardless of what you think about whether this is a good or bad rule (and I tend to agree it's a bad one), no one is served under any interpretation of the rule by disallowing celebrities from posting under their stage names.
Basically, if it's an exception to the rule, then it's a sane and well-justified one. If it's a subtle edge case, then so be it. I think it makes very bad evidence of hypocrisy on Google's part.