Ditto that this is a drill I've seen used over the years. Seems like your son could tell you pretty clearly that it was a drill, as opposed to a "new swing" that the coach is changing every player to? Players often look silly trying new drills that are designed to isolate/exaggerate a certain movement, rotation, muscle memory.
I was alarmed because it appeared the coach was correcting some of the players during hitting practice on the field. I heard him say "let the forward momentum carry the ball farther".
I would like an explanation how that drill helps in any manner whatsoever?
I would want my kid to practice a drill that he can use at the plate.
The good news is I just got back from watching practice and my son was hitting off of live pitching and using the correct technique. 