Lockdown

[SMEngmann]

Can someone explain to me the logic of "locking down" in 3 person mechanics? I specifically refer to NFHS and NCAA mechanics where last second shots are judged by the official opposite the table. Some advocate no rotation for the last 30 seconds of each quarter/half, and others say the lead can move, but L's movement in that period doesn't dictate a rotation.

My question is plainly why? 3 person mechanics are designed to put the 3 officials in the best possible position to judge plays, yet we abandon them for the most crucial plays at the end of the game. Please, someone, explain the logic of doing so.