I believe AB's point was that you have to have a legal catch before you can determine forward progress. In your play, the receiver does complete the catch by touching inbounds; in his play, he doesn't.
Exactly. Forward progress is determined by the foremost point after POSSESSION, but not until a catch has been made. A player that never lands inbounds hasn't made a catch, and isn't entitled to forward progress.
Take your "catch" in the end zone. Diving (airborne) receiver possesses a pass while in the air over the end zone. He lands on his belly and the ball, which is under him, pops loose. Are you going to call a TD because he possessed the ball over the end zone? Or a leaping receiver jumps and possesses the ball over the end zone, but lands beyond the end line. Touchdown? Of course not, the passes were incomplete, because the receiver never touched inbounds, thus completing the catch.
Same with your play. It's not a TD when the ball was possessed, it didn't become one until he completed the catch. Under FED rules, a player that never hits inbounds, whether pushed or carried, hasn't completed the catch. The rules committee had a clear intent when making the rule: eliminate the judgment of whether a player WOULD have landed inbounds. They did NOT want to duplicate the NCAA rule, then wanted a clear, less judgmental issue: either he did or he didn't land inbounds. HOW he did or didn't wasn't supposed to matter, until the writer of the case play muddied the waters, against the wishes of the rules committee.