Why does the DC resistance measurement function of the 4287A require to be calibrated at the same time with Open/Short/Load calibration?

The specified accuracy for the DC resistance measurement is applied when the Open/Short/Load calibration for the DC resistance measurement is performed. Normally, since the Open/Short/Load calibration routine for desired measurement points can be also used to take the calibration data for the DC resistance measurement, the DC resistance calibration is executed concurrently with the Open/Short/Load calibration for the desired measurement points.