In the one end of summer tournament I work at, the officials generally don't strictly enforce it. If they see it, they'll tell the players to stay off the rims and if they still keep it, they warn them that the next time may be a T.
In 8 years of working at this tournament, I can only recall a single T for pregame dunking. Our main concern is making sure each team has 5 players ready to play and that they pay the refs before the tip off
