That's because in rugby there's no easy metres from dummy half. That's all this rule will encourage.
'Roll away immediately' = offside markers. Why wouldn't you run from dummy half every time?
This is the major legacy fault that rugby league needs to address. The play the ball was never intended to be fast. And without markers it's a boring, repetitive game. More important than ensuring quick play-the-balls is ensuring there are viable alternatives to the dummy half run.
Maybe the rules of the game need to make explicit that the defenders making the tackle are excluded from being at marker on the next play. That takes away the implied mandate of those players to attempt to get in to marker at any cost, and force defences to adapt and bring other defenders into marker while the tacklers from the previous play just try to get themselves back onside without interfering with the attack.
That should open up gaps out wide rather than at marker, and this will encourage shifting the ball over repeated running through the middle. But the rules need to change to make clear that tacklers have no right to be at marker on the next play. That removes the huge grey area as those tacklers try to get there before the dummy half does.
