[aschen]

No expertise, but I suspect the relationship between throttle position sensor and and throttle body opening is complicated.

I assume it changes with temp, settings in the car (sport, econ, etc), adjusted by what the ECU has learned. There could be a time element built in, like so many modern cars have rev hang. The way I understand throttle position in modern cars is "torque demand" and how that request translates to throttle opening is translated by a bunch of factors and the whim of the calibration engineers.