Obviously, if the ref thought the man dived he wouldn't have awarded that penalty, and he'd have booked him. The question was whether that was a dive with him succeeding in deceiving the referee. After all, deceiving the referee is always the intention of any player making a dive.

Here it is on YouTube Looks like a dive to me.

If it is determined after the match that a player did deceive the referee into going a penalty, it is obviously too late to penalise this in the normal way, with a yellow or red card. Suspension is the only remaining way of penalising him.

"Lucky Arsenal" as they say.