Quite frankly, I don't think it matters at all what WotC writes down for "group stealth" rules, because it seems like that's one of those situations where every single table just came up with their own houserule to cover it anyway. Regardless of what gets written, almost every single person is going to think it stinks and is going to change it at their own table. So at the end of the day, it just comes down to an e-peen contest so to be able to be the one that says "Ha! The rules I like are the ones in the book! The other 95% of you can just make your own!"