I have a Comma 3 in my car, and it has a calibration phase that takes like 3 minutes of driving. The device works for many different cars of different sizes, and their driving algorithm uses neural networks. As far as I know you still have to get the device fairly close to centered on the windshield for it to work, but clearly you can still do some sort of calibration based on driving data alone. Maybe Tesla can account for even more deviation in camera position because they know ahead of time where the cameras are mounted?