I was reading somewhere that Teslas have unreasonably tight tolerances already, but they never acutally check them becuase the parts would inevitably fail and it would grind production to a halt and cost them a fortune. The reason for the tolerances is becuase people keep complaining about the spectacularly shitty fit and finish of the cars, so someone at Tesla (probably Musk himself) just ordered that the tolerances be tightened without changing anything else about the production process.

I guess they have tightened them so many times that now he is demanding less than 10 microns.