Byron Nelson -- the original Mr. One Piece -- started his Stroke from the Swinger's Classic Adjusted Address Position. In other words, his Left Wrist was Bent and his Right Wrist was Flat. As he moved away from the Ball, both Wrists retained their respective alignments well into the Backstroke. That is the 'One Piece.' Add a little flexibility of 'lag and drag' and, on video, Byron Nelson clearly evidences the 'Lagging Clubhead Takeaway' of Homer Kelley's as yet unpublished seventh edition.
As always . . . I took your advice and purchased Byron Nelson's Winning Golf off of e-bay. I agree with the above analysis. I'm not sure that Mr. Nelson's takeaway was a SHOULDER TURN TAKEAWAY based on a review of the pictures. It looks like the Lagging Right Forearm Takeaway to Bucket.