Look back rule

[jmkupka]

Originally Posted by teebob21

Bingo. If she's doing it to "threaten" the runner, it's a play and LBR is off. Taken to its logical extreme, we could stand there all day legally, with the runner off base, and F1 in the circle with the ball poised to throw in an epic staredown.

And my take is, I dont feel the ball at the shoulder is to threaten, it's more to communicate "If you take off, I'm ready for you". That's not a play.
Unless she cranks back to throw, the onus is on the runner to make her choice in a moment or two.