Reflecting in my comment, it’s more for hooks than pulls. When you’re hooking from a square stance, you need to get the shoulder out of the way, and the natural arc of the arms and bat momentarily gets between you and the ball. GP says it’s why Crawley struggles with the short ball so much. With open shoulders, the leading shoulder is already out of the way, so your arms don’t need to take the same arc, and it eliminates the blind spot. Well, it does for me anyway, and slow mo vids seem to prove it too. I’ve perhaps not explained it properly, but then again I’m not a coach.
I still don't get this. (edit: sorry if this seems grumpy it isn't meant too! I see Gary Palmer has his advocates and I am trying to understand his method, which is more than stand more open I know).
As a side on player, when you get a short ball, your back foot moves back and across, this opens you up to be able to play the pull, duck or sway out of the way.
If you are front on you don't have the duck option and the sway option isn't easy. You are just a target, which is why Sibly looked ungainly against the quick stuff, but he does have a method.
I have spent a bunch of time being coached on the short stuff because I was being peppered in one of the games I play annually. (the coach has seen me play a few times and knows that anything in my half my be in my arc and tells his bowlers to not bowl full at me...! Thanks Medders.)
When I started the session I had my back foot prepositioned outside the off stump and bat raised. We then hit a few and moved to a normal stance and movement with bouncier balls then proper balls (Reeds School has all the gear...)