He is trying to score a try. He is playing at it. Same as when a player is diving for the ball and then has it hit or kicked into his hands or arms, he is still playing at the ball even though it is a rebound. You see it all the time in video ref decisions when two players are diving for a grubber.
Say in the Stewart no try, if Thaiday hit it into Stewart's arm or hand instead of grounding it, then it came forward off Stewart's arm or hand into the ground, then Stewart grounded it, it's a clear cut knock-on. Even though Stewart isn't 'playing at the ball off Thaiday's hand' like Karl's stupid arguments, he is still playing at the ball. Same with the Inglis one. If you are playing at the ball, trying to catch, ground, hit, rake or whatever, and it comes off your hand or arm it is a knock on.
Say in the Stewart no try, if Thaiday hit it into Stewart's arm or hand instead of grounding it, then it came forward off Stewart's arm or hand into the ground, then Stewart grounded it, it's a clear cut knock-on. Even though Stewart isn't 'playing at the ball off Thaiday's hand' like Karl's stupid arguments, he is still playing at the ball. Same with the Inglis one. If you are playing at the ball, trying to catch, ground, hit, rake or whatever, and it comes off your hand or arm it is a knock on.