Gary,
I almost always agree with your comments, and particularly with your statements above, with one minor exception.
I find I am puzzled by your comments about PSD divers seeking further training. I find that I can't quite see how Divemaster training and practice which is designed to improve a diver's overall performance, could intrude on the work that he or she must do as a PSD.
It is true that student training does not, of necessity, occur in black-water situations. I would have to say, however, that anything which tends to increase a diver's skill and comfort level in the water is, by definition, a benefit!
Perhaps, howver, I am mis-reading your comment. Could you elucidate?
BJD