Perfectly legal play. I think that having the player fall down ****ers the defense to go for the "easy out" and that gives the runner on third the chance to score. Also, seeing something out of the ordinary can make a player pause an extra second or two to process what they're seeing and that also can buy time for the run to score.
Here's a couple more you might see once in a blue moon, but if you ever do see them you won't be able to say you never heard of them before!
- Runners on first and third. On release of the pitch, have the runner on first take her lead off about 20 feet down the right field line, out into right field! This is legal- the rules don't specify which direction the runner has to lead off. It's not "leaving the baseline", because the runner isn't doing it to avoid a tag by a fielder.
As long as she adheres to all of the other requirements of the Look Back Rule, the runner isn't violating any rule with this strange lead off. It will often draw a throw for the "easy out"- or just confuse the heck out of the defense!
- Runner on second. Have your catcher attempt a pick off following a pitch. If the runner is diving back and does not see the ball, have your shortstop yell, "Go get it!", while your second baseman runs toward the outfield as if chasing an errant throw.
Only the shortstop has caught the ball! If the runner bites, thinking the throw got away, you might have an easy tag play if the runner decides to go to third, or comes off the bag to locate the ball.
If you ever decide to try one of these in your games...please don't mention my name!