The "Privileges" field that states "Administrator" or "User" is the base priviledge, i.e. base type of account. A user may be in local administrators group on this or that PC, but it's still a user in general, not administrator. For the purpose that you describe we have already tried to add a "Group membership" field for user accounts. But it appeared that the collection of group-user relationships is causing high load on the domain controllers and is leading to inappropriate increasing of scan time. So we were forced to disable this possibility until a resolution is found.
EDIT: This is my 500th post here