The commentator, myself and many others would disagree strongly with your assessment that the pass didn’t leave Garner with anything like a good chance. “It is set up beautifully” were the commentators words.Well I’ve seen great passes from one yard to over twenty yards, not always necessarily creating a goal but taking two or three men out of the game, sometimes giving them clear chances, but you’ve seen the goal we are discussing and that pass never left Garner with anything like a clear chance, it’s not the length of the pass but where it leaves the scorer with a good chance of putting the ball in the net.
And I have seen no generally accepted definition of assist, anywhere, that limits them to “only where it leaves the scorer a good chance of putting the ball in the net”.