Clip 2 12 April 2019 - Law 16
The Lions have the ball. From a tackle/ruck, Wilhelm van der Sluys of the Lions passes to prop Sithembiso Sithole. Luke Stringer of the Sharks grabs Sithole who lowers a knee. The referee calls "Tackle!" and the Sharks release Sithole.
The ball comes back to Ross Cronje of the Lions who charges ahead a short way but is grabbed by Stringer and Louis Schreuder. Cyle Brink drives into the group to assist Cronje. Cronje is battling to get his knee to the ground but the referee announces: "Held up. Maul first", and, when it falls down, the referee awards a scrum to the Sharks.
Commentator 1: "A very different interpretation of the law."
Commentator 2: "Once the knee hits the grass, a tackle has been effected, but very different ideas from Mike Fraser." [Fraser is the referee.]
There is no interpretation in this, just application of the law. The knee hitting grass does not mean that a tackle has been effected.
What it takes for a maul to be formed, is crucial.
Maul: A phase of play consisting of a ball-carrier and at least one player from each team, bound together and on their feet.
For a maul Sithole's knee needed to hit grass, before any other Lions joined him. That is how the referee saw it and so he called Tackle.
REQUIREMENTS FOR A TACKLE
1. For a tackle to occur, the ball-carrier is held and brought to ground by one or more opponents.
2. Being brought to ground means that the ball-carrier is lying, sitting or has at least one knee on the ground or on another player who is on the ground.
3. Being held means that a tackler must continue holding the ball-carrier until the ball-carrier is on the ground.
In the Cronje case, the referee judged that Brink joined in before Cronje's knee hit grass. That meant that a maul had been formed before Cronje’s knee hit grass. That meant that the laws of the maul had to be applied - and a maul does not turn into a tackle. The maul ends in this case when it collapses and it - the maul - becomes unplayable, and then the scrum is awarded to the team not in possession at the start of the maul, which started when Cronje was carrying the ball.
It would seem that the referee was right and the commentators were wrong and broadcast misinformation to many.
It is dangerous to try to oversimplify the laws.