Rules are always general, but each body is specific in its strengths, needs, and resources. Absolute rules are never absolute for everybody....only an idealized version of all of us, but hardly always true for each of us (whatever the heck that means!).
I find that I move forewards and backwards on the saddle just for variety and to relieve specific pressure points-- as do we all. Right there I've just thrown off the absolute KOPS: my below the knee bony protuberance thingy is pushed or pulled off KOP. Not to mention, a static position invites overuse or sooner onset tiredness. Small angle adjutments can be refreshing.
George, don't be slavish to rules of fit... they're just guidelines. Experiment for what seems to work best...i.e. avoids pain, seems most efficient for you, and is most comfortable. Keep in mind that Peter White has fairly severe arthritis in his back.