Just because it is not working like you want it to, does not mean it's wrong. This type of functionality is built into vBulletin,
is_member_of and is working as intended by the vBulletin developers.
As far as I can tell it has been around at least for 11 years,
http://www.vbulletin.com/forum/forum...94#post1310794
So before you go around telling people how things are supposed to work, or that they don't have a clue what they are talking about, I suggest you do your research.
You have two developers here, that have a total combined modification release of 315 +/- so I would think they know what they are talking about versus someone who has no modifications released.