I agree this is a catch. But my focus is on finding out why we didn’t get it right.
The streamed clip I saw did not show the back judge, and this was his call 100%. I looked at the Hudl video, which does show a wide view. The back judge is in trouble right away because of his initial position. He is head up on the football ... which is all the way on the left hash. To compound the problem, the formation is strong -- with trips, no less -- to the linesman’s side. The back judge’s initial key in this formation is the widest receiver in the trips, so he needed to line up accordingly. B should at least be in the middle of the field in this situation. Instead, he is running along the end line trying to close on the play when he has to make the critical call. On a bang bang play like that, you want to be stationary when you’re processing what you see. See, those mechanics rules do serve a purpose. 😉