It is possible for the group of a child prim to differ from that of the root prim. To build such an object it must first be unlinked, the groups set, and then relinked. Rezzing an objects resets the group of the object to that of the group that the user currently has activated. Changing the group of an object changes the group for the entire object. This may only be an artifact or manifestation of VWR-5044.