In extreme cases gears can change themselves when the rider applies high torque out of the saddle.
Mills often used such gears to apply torque in the required axis.
A properly executed lock of this type does not apply torque to the wrist, itself.
Without the reaction arm to prevent rotation of the outer casing, the output shaft cannot apply torque.
These also use a rotary hammering action to apply torque to fasteners.
It employs the principle of applying torque to a deflecting beam rather than a coil spring.
This key is then struck sharply with a hammer whilst applying torque.
This would apply more torque and stability to the hold.
However, it is winding current, not voltage that applies torque to the stepper motor shaft.