Where the ball last left the area should be in the direction and vicinity of the receiver, so even if it goes five feet over Branch's head on the sideline (e.g., into the stands) it's still in his "direction" right?
I guess it may be that the "vicinity" interpretation is a little murkier when it comes to the sidelines or the end zone which may be why you don't see much enforcement there, but if you chuck it upfield, and it hits the middle of the field with no players nearby, I would guess that's easier to enforce.