The situation was that my DD who is the pitcher was standing behind the rubber getting her signs and the runner on 2nd takes off. Since she was not expecting this and the 3rd baseman was playing in, the runner was safe. The opposing coach said that he picked this up from another coach who said he did it all the time.
As has been stated, the pitching plate has nothing to do with the rule. If the pitcher has the ball in the circle and is not making a play, any runner off base must immediately advance or retreat to a base and if on a base they may not leave the base.
I am assuming your daughter was not tossing the ball in the air, or tieing her shoe, messing with her hair with the ball under her arm or between her legs? ASA requiars posession and control of the ball by the pitcher, all other rule sets are just posession.
"Immediately" does not mean quickly so a runner who is moving slowly toward the next base is not in violation of the LBR. And technically, a runner isn't required to commit to advancing or retreating until after their allowed stop.