I never knew that was a thing.
off the internet:
Angle Controlled Tightening
This method, also known as turn of the nut method, was introduced for manual assembly shortly after the second World War when a certain tightening angle was specified. The method has been applied for use with power wrenches, the bolt being tightened to a predetermined angle beyond the elastic range and results in a small variation in the preload due, in part, to the yield stress tolerance. The main disadvantages of this method lie in the necessity for precise, and, if possible, experimental determination of the angle; also the fastener can only sustain a limited number of re-applications before it fails.
so the torque wrench is set to a figure coinciding the likely elastic range and the angle turn then sets the pre-load very consistently.