Don't know. It depends, primarily, on the coefficient of elasticity of the particular alloy used and the cross-sectional area of the fasteners. They seem well enough engineered that there must be a certain rhyme and reason for the specifications given. Usually (not always) a good idea to not second guess the people who engineered something. I guess, in this case, the first question I'd ask is "Have we experienced any problems torqueing the screws to factory specs?"
Jordan said it better than I could. "We have experienced problems torqueing the screws above factory specs."
The problem wasn't with the screws, however. Which leads me to believe the torque specs are in fact based on the compressive strength of the parts being compressed, which is the limiting factor.
Contrary to your first post above.
