I believe people are annoyed that if you grant "ulx banid" to an admin, they can then ban superadmins, even though this is not allowed via "ulx ban". This was an intentional gap originally, since we supported adding users by several different methods (not just steamids), so there was no simple way to know if the targeted steamid was a superadmin or not.
Today, it is possible to know if they are a higher-level admin, but the gap remains. Traditionally we've recommended people not give "ulx banid" to people they think might abuse it, but annoyance continues to abound; we are sympathetic. I know exactly how this could be supported in the current ULX, but the risk/reward is low enough that we are punting until ULX4.