True, but usually just the weight of your arms applied on the hand is enough to issue micro-turns to the wheel.

I believe the detection relies on torque + angular position (the model S manual says it will sense resistance to wheel motion as well as motion itself), and the latter should be more more sensible because those mechanisms are usually made of encoder-motor-high ratio transmission-load, so a small turn on the load gets multiplied 10-100 times by the transmission before being sensed by the encoder.

I guess the lack of precision comes from Tesla wanting to avoid false positives