ZM I would agree with that. I don't mind the left arm getting a little higher than that, but that is the feel and position that I try to get my students into to feel the shorter swing. Thanks for that ZM that is a great referance point to develop the feel!
I use one, all the time since I'm physically not able to twist due to herniated discs and a blown out knee that's bone to bone. You can still make a mild shoulder turn with a back-swing that go back to parallel to the ground. Being able to un-cock your wrists at impact is what will help in not losing much if any distance if you are comparing this type of shot against all of your other shots including the ones that are a fairway over or in the woods. I try to hit a draw so my right foot is back a little bit and that helps in the mild turn.