I do hear what you are saying, and I believe if we lived in a perfect world with incredibly precision made instruments, you would be right on the money, but we don't , and when you factor in all of the mechanical imperfections of the guitar and the limitations we have for adjustment, the distance this node moves is very small, when we consider our target area is the width of one fret, and the size of the contact surface of the finger tip , I think the movement of the node is practiclly imperceptable, I can't ever remember one time in 23&1/2 years of playing of not being able to find the harmonic at the 5th, 7th or 12th fret and even if I did, the brain can quickly compensate and make this incredibly small adjustment, I played violin for awhile and even with out aid of frets you quickly learn how to play harmonics on open and stopped strings, so I guess I could sum all this up by saying that even the raw beginner without the aid of any technical understanding would without thinking about it just make the mental adjustment and find that node easily..........