Read the threads that were linked by snap0964. It makes sense. The higher the torque the more inaccurate the torquing is, due to friction and something else. So by torquing the bolt up at a lower torque setting decreases the inaccuracy of the torque wrench, then tightening the bolt up a further 90/120 degrees will tighten all the bolts up evenly since 90/120 degrees can't really have errors (unless you are judging by eye).

phong =P~

i see wot u mean by takin the inaccuracy out of the torque wrench.

use to torqueing aircraft components were calibration is checked monthly

Has nothing to do with the accuracy of the torque wrench.

Its the proceedure.