Holding the ball in at the scrum is a smart tactic and we should never have stopped the loose-forward from being allowed to do it.
If the opposition can be kept 'honest' (i.e. bound-in in the forwards and onside in the backs), we may see more expansive play from the scrum. It would give the scrum a 'modern purpose'. (I'm not one of those who wishes to return to the mess we used to have with so-called 'competitive' scrums and which rugby union are now finding a royal pain in the backside).
One of the criticisms I hear levelled at RL is that it can sometimes be a bit one-dimensional. Having handovers instead of scrums would make it even more so. The scrum having a modern purpose helps to counter this.
I'd be tempted to ramp up the potential benefit of chancing your arm from a scrum a bit further by having a think about other ways of creating space for the backs. For example, does a scrum pack have to consist of only six players?

I must be really old.
Pushing at the scrum or delaying the ball coming out are not new things. They've been around forever. It's just that the rule changes/adjustments around the scrum meant it was better to take advantage of the quick ball from the scrum. If the ball can be put "behind the props leg" then the ball is in and out in a flash. No point pushing as those players need to be defending.
Teams tend to follow each other in style and it looks like it is just the done thing.
They are not taking advantage of the rule, they are taking advantage of the other team following such a regimented plan that they are not playing what is happening on the field, they are just doing what they were told in training blindly.

I think there's little chance of us going down the union road, because the focus and importance of the scrum are so different. In RL there is always going to be the emphasis on breaking as quickly as possible , whereas in RU there is a huge focus on the initial 'hit' and drive as a way of one pack or the other asserting dominance over the other. In RL we tend to assert dominance in open play with the big hits.

Doesn't it just expose the fact that players aren't waiting for the ball to come out before breaking/advancing?


Exactly this. If it was the other way round there'd probably be a thread bemoaning Wigan breaking early at the scrum.

The other side to this is that the defending team will now break less quickly, giving the attacking team more chance of scoring from a scrum where the ball isn't trapped. It returns scrums to the reason they were retained, to provide another attacking option, and gives the greater advantage to the team that hasn't offended to create the scrum.

Have Wigan broken 'The spirit of the scrum'?