Disconcertion

[BTBaller30]

I am curious about the disconcerting of the free throw shooter rule. I saw a situation the other day where a player was standing at the bottom section(on the block) before a free throw and held his arms above his head. He didn't move them throughout the entire process from the time he got set on the block till he started his boxout after the 2nd shot. The next time a shooting foul occurred the head ref told him it was disconcertion. I disagreed because he never moved or spoke. He just stood there. I am just curious about the rule.