We don't know that, he's defending and challenging for a ball with an offside player. If he has a free run at it he might get there.
You can't be offside and attempt to play the ball whilst challenging an opponent so someone else can play it. If that were allowed you'd have players just standing in offside positions blocking defenders from going for balls.
I agree that the rule is badly implemented, this whole active and non active stuff is open to subjective interpretation for each incident.
I played a game not long after they updated this part of the rule, ball came over the top, I went out to play it, player who was miles offside went for it too. He blocked me off as we both got there, then another player who wasn't offside came in and took the ball. All 3 of us were within a foot or 2 of the ball, referee allowed the goal, because the player who wasn't off played the ball, even though the other guy impacted my ability to play it. It was a load of bollocks and I got booked for letting him know what I thought of the decision.
Personally I think in situations like that free kick if any player is offside inside a crowded box, the flag should go up. Puts a stop to all this nonsense.