I have seen brushless ESC's that starts in low RPM in sensored mode and at a certain RPM switches over to sensorless, The GM120 can do that. Switching fequencies I have not seen but I do not think that is the solution to prevent cogging. Cogging happens when the ESC can not reed the rotor position and basically that happens at low speed because the slow movement of the magnetic rotor along the stator will not create much voltage to sense. It is like an altenator which its voltage is depending the rpm speed.

With a magnetic rotor (synchrone brushless) you do not want to happen that the rotating field by the stator is out sync with the rotor speed. That can give huge current peaks and a kind of back fire That is why the position of the rotor is sensed to be sure that the rotor and stator rotating field stays synchronized.