When I was playing if you were tackled and the ball touched the ground it was a ruck and the ball had to come out using feet. The tackler could not handle the ball and both should roll away. An offload was only allowed if the ball had not touched the ground.
Yesterday the Scottish player was tackled and, with the ball in hand, it touched the ground, he then rolled over and did the offload to Van de Merwe.
Only one of the experts mentioned that it "might have been" against the rules.