Per 1-L-2, the head is allowed to turn (but not sway or bob), but surely this rotation will change the way your eyes look at the ball. Doesn't this make the "eyes argument" obsolete, as I do not know of any great golfers who does not turn their head slightly on the backstroke? Unless, of course, you can tell the difference between a head turn and a head sway by using your eyes, which I certainly can't.
I can honestly state that the majority of photos I have seen do not support either position.
I also wonder what the definition of the base of neck is? To me this is a point on the spine that the shoulder move up and down from, the head moves or support head movement side to side without tilting the spine.
Isn't the ideal motion and alignment to be that the motion is around the spine between the hips and shoulders?
Head movement caused by the pivot should not be considered a head in motion. Head movement independent of the pivot would be a fault or potential fault requiring adjustments during the golf stroke. Intentional head movement is often associated with bobbing and swaying, not the only cuases for this.
Minimal movement does support a stable platform and maintaining balance. This inturns supports the golf stroke alignments and minimizes any adjustments that need to be made.
Could be wrong, but back in Jack's day the pre-turn head was an option to raising the chin, both allowed the shoulder to pass without the head getting in the way.