No! That is not a bug in the "if" statement. The so called bug is not a bug, its doing what it is intented. The reason you think its a bug is because you dont understand it.
Connections[GetConnIDX(UCID)].IsAdmin
That code returns a byte and its upto you to work out if they are an admin or not. if that returns 1 then they are. If it returns 0 then they are not. You cant just send that in a button and expect it to show everyone who is admin. The code that robbo posted will only show a button to a NewConnection if they are admin, Even then it will only report there admin status on the server. So please learn before calling this a bug.