I really don't like coaches who do this.
Maybe he was a former drill instructer and he is anal about uniform rules.
A coach who does this may start a tit-for-tat exchange. Imagine now if the other coach calls you over for a conference and states that one of the lineman on the other team doesn't have his shirt tucked in. Or a player's sweat band is too far up the wrist, or the other coach isn't holding an authorized conference, or they have too many coaches in the box, or the coach is coming onto the field to call plays, etc.
I'm with Bob. I wouldn't want to be running that game.