In order to ground the ball in goal, a ball carrier must touch the ball on the ground while in holding the ball
[LAWS]Law 22.1 GROUNDING THE BALL
(a) Player touches the ground with the ball. A player grounds the ball by holding the ball and
touching the ground with it, in in-goal. ‘Holding’ means holding in the hand or hands, or in
the arm or arms. No downward pressure is required.
[/LAWS]
In order to ground the ball in goal, a player not carrying the ball must "press down on the ball".
[LAWS]Law 22.1 GROUNDING THE BALL
(b) Player presses down on the ball. A player grounds the ball when it is on the ground in the
in-goal and the player presses down on it with a hand or hands, arm or arms, or the front of
the player’s body from waist to neck inclusive.[/LAWS]
This is something that commentators (especially Justin Marshall) continually gets wrong; not understanding that there is a difference between the grounding of a loose ball and a ball that is being carried. I don't expect referees to get this wrong as well.
The Gold player handing the ball back does not ground, or attempt to ground the ball. He is holding the ball off the ground with a hand under the ball and a steadying hand on top; I'll bet he didn't even realise he was holding the over in-goal. I have absolutely no doubt that had RH immediately ruled 5m scrum on the basis that this player grounded the ball, Gold would have complained that their player had a hand under it.
The Gold player acting as halfback doesn't press down on the ball, he puts his hand on the ends of the ball and is about to pick it up when Red 4 pounces.
Bouqets to Red 4 for knowing the laws and realising that the ruck ends in-goal and the ball was available to be played, and brickbats to the Force for their ignorance of the Laws. The learnings for them here is that, when the ball is in-goal, don't faff about, ground it.
There is no downside for players in knowing and understanding the LotG
On a side note, I thought RH had a shocker with regard to his scrum management. Many of the problems were of his making because he was not allowing the dominant scrum to dominate. Three times that I counted (two with Gold throw in and once with Red throw in) he told the SH to put the ball in when their scrum was already moving backwards. These should have been FK/PK for early shoves. two in favour of Gold and one in favour of Red.