You are all passing judgement on the initial ping-pong passage of play strengthened by your intense dislike of SB, who incidentally is a very good commentator particularly on the subtleties and technicalities of play, and your understandable support of the referees' decision.
If you look carefully at the slo-mo the decision was made not on possible knock-ons, which the ref appeared to be OK with, but on the consideration of a possible obstruction with the offside team-mate.
Did he prevent the immediate opponent from stopping the grounding?