With a closed or neutral stance where they are is pretty much where they will be. With an open stance it is less predictable.
I may have misspoken, I meant for the batter to be able to adjust accordingly. a coach unilaterally requiring a player where to stand in the box interferes with the batter engaging in the mental game. "Stand here and hit the ball and if you don't get a hit it's your fault". why make everyone adjust before you have even seen what the pitcher throws?
With a closed or neutral stance where they are is pretty much where they will be. With an open stance it is less predictable.