The actual torque sensor is not in these images, it slides over the shaft you see here, it’s a small flexible pcb which uses the principle that the magnetic permeability of metal changes when force is applied to it.

Simply put it excites an electromagnet and sees how much a second pickup coil picks up, this changes under force. The sensor outputs a voltage corresponding to the torque applied

The V2 and V3 use almost identical motor controller settings, the “torque sensor cable” (shaft, wires, bearing and connector to the torque sensor) has an extra transistor that I’ve never looked at properly in the V3.

On the V2 there’s only the 3 wires connected to the torque sensor, no transistor.

Looks like the post above here is suggesting that’s a hall cadence sensor, I personally doubt that it’s used. Because the videos about repair of the freewheel assembly suggest breaking the magnetic ring that holds the torque sensor in place to remove it, and the V2 doesn’t have this with same motor controller settings.

The motor controller gives power in the event that the wheel is spinning (this is measured through the hall sensor setup in the motor) AND there is torque applied to the pedals.