Audiofeil, thinking about it again and I agree with you, even if your nick means "audiowrong" translated directly from Norwegian (sorry, just had to mention it. Forgive me).
We all know that the VTA is of great importance for the VTF, especially with dynamic force.
My writing might be based on the fact that I do not remember well enough. But, could it be that the combination of headshell and cartridge would influence on how precise the dial is if you have the VTA set different from the angle in witch you outbalanced the arm. I have some problem explaining this in English and I dont think it is it of great value anyway.
The dial is in my opinion consequent, but the numbers on it is meant for reference not correct value.
Sorry I couldn't explain this any clearer.