I don't, I'm attempting to rationalise your analysis. There is contact between all parties in the middle, yet, contrary to your proposal, Sharp, who is in an offside position when the ball is played, can be deemed offside the moment he pulls Vyner's shirt (pic makes it clear that he did), ergo, interfering with an opponent, i.e., making an obvious action which clearly impacts on the ability of an opponent to play the ball. It's not as simple as you make out. It isn't an either or based on your interpretation of the law. That aside, Tanner is in the wrong position and should be marking the scorer.