It's actually an over-officius interpretation from both state associations, which some officials have become over-officius in their applications of it. Situation happened in a game last year where B1 was walking off the court at halftime, and was just a couple of feet from the door to the locker room hallway when the official spotted him pulling out the shirt (just as a comfort thing to be "loose" for the halftime chalktalk) and T'd him up for it.