Originally Posted by sclim
I stepped slowly through your description, and from what I understand, you are saying that you can get the similar effect of arm pronation (internal rotation of the humerus on the glenoid fossa, i.e. the "joint" of the scapula)...
Oops, I said it wrong. I meant internal rotation of the humerus.
Pronation, of course occurs below the elbow, and would not help to achieve a vertical or near vertical forearm, which would require the axis of the elbow "hinge" to be rotated to as close to the horizontal line (when in swimming position) as possible.