We have all seen this rule most commonly applied by Nigel Owens. He never quoted it, but inferred it many times, for example, when suggesting a player faking injury should come back next week (for a roundball game).
All the ref had to say was, 'Touch it down so the crowd can watch what they paid to see.' No threats or any penalty. A simple instruction to get on with the game.
The same with the Hoo-rah calls on winning a scrum penalty.
My view is that scrums are a way to re-start a game, not win penalties. As we saw at the Lyon game. Not the way we saw on Friday. As soon as the ball is won (it gets hooked), the ref should call use it. As soon as 'Use it' is called any collapse of popping up might results in a reset if the ball gets trapped in a melee, otherwise, on we go.