I believe it's spotting the difference between deliberately sacking a maul, and simply failing to keep your feet in the tangle of legs and bodies; and sending the right message to the ref.
Mauls are also hard to set up correctly, even with your entire pack around you in a controlled manner, and especially so now that you have to move the ball backwards, not the ball carrier. Setting up a maul in open play must be damned-near impossible to do whilst protecting the ball; and if you fail, you turn-over the ball. You used to see it a lot more (and still pretty infrequently IIRC) in the olden days when the team moving forwards gets possession, so the only trick was to start it with momentum.
Bear in mind, that's all my interpretation, and as a SH I was always in favour of just letting them get on with it, and to make sure the fat boys remembered not to eat the ball.