Out of chaos comes clarity.
Out of complexity comes simplicity. Necessity is the mother of invention. And thus evolved the short cut balance.
There are usually advantages and disadvantages to any modality. It seems to me that the only disadvantage of the short cut balance is that it is not appropriate for a skeptic.
I started doing the short cut balance out of necessity–the necessity to simplify, save time, save energy for myself and the testee, and to enable me to test without a surrogate. The fact that untestable muscles can by tested with the short cut method is an added advantage.