I have been practising what I call a "no arms swing". My shoulder turn starts the pendulum of my arms going back, sort of bumping them up to but not past my right shoulder. I am not consciously thinking of my arms and hands at all so I guess it follows that I am not swiveling at all. My leading hand feels like the knuckles are folding under and at the top I have a sort of spring action as my right wrist bends all the way back and then recoils a little. As long as I don't think about my arms and just turn my body, my chest traps my arms and kind of pushes them into impact where I hit the ball beautifully. I get the underarm throw sensation with my trailing hand.
I'd be very interested to know, in TGM terms, what kind of swing this is so I can look it up in the book?