How could a dental lab micromotor start at high current and torque without damaging anything?
The PWM speed controller could be doing a soft-start every single time you push the pedal, just one that is too fast for you to perceive.

The other thing is giving the motor time to develop speed is good for long life and efficiency but we need high torque at moment to carve agates,

Do you actually apply the micromotor to your workpiece prior to pressing the pedal? Or crash your microtool under speed into the work piece? I doubt it.
Instead, I bet you press the pedal to turn the tool on and then gradually move it into the workpiece. That means the motor is only starting up under the torque due to its own inertia rather than high torque due to load. And the fact you gradually pressure to the workpiece means that the load torque is introduced over a period of time (and having inertia already built up helps too).
In which case, it might not even need a soft start to prevent current inrush.