[FBALL]

I just found this:

College and pro rules, with regard to ineligible linemen downfield, are different. The pro rule restricts linemen from advancing beyond the line of scrimmage until the ball leaves the passer's hand, whether or not the pass crosses the line of scrimmage.

The college rule only restricts linemen on passes that go beyond the line of scrimmage. On screen passes, under NCAA rules, linemen can advance beyond the line at the snap without penalty.

A shovel pass is considered a screen pass, thus the "behind the line of scrimmage" rule applies.

I did not realize that. I believe the high school rule requires linemen to stay until the pass is thrown.