I'm not so sure, the arsenal decision was wrong because no advantage was played at all and subsequently having failed to play advantage the correct punishment to Sanga was not delt delt out.
However in this case assuming the ref saw the foul and in the extremely short time available decided to play advantage which I highly doubt, a shot on goal was attempted, that was the advantage. The fact that a goal wasn't scored or the target hit is not a reason to pull play back for a penalty. Though what should have happened in that situation was play stopped immediately and a penalty awarded (even though there wasn't time to humanly do so between the foul and the shot) as arguably shorts around the ankles negated any meaningful advantage