It's a simple enough rule in theory, unfortunately it comes down to making a judgement call about a player's intent which refs are never going to get right every time. In this case, Longelo wasn't even facing the ball half the time it was in the air from the corner, and by the time he was facing it there was no way he could play it as there was someone else in the way. So I guess that's why they decided he wasn't making a genuine attempt to do so.