My car isn’t a Tesla, and the dashcam has a “parking mode” that records everything while parked. So, do that, don’t get a Tesla, and never get towed to access the camera.
If the police sees the dashcam and suspects that there's footage on there, they can apply for a search warrant and seize that footage as well. It's unclear why they needed to tow the tesla in the first place. The article says that the footage is on a USB drive, so presumably they could just pull it out and make a copy. If they're towing it because they couldn't locate the owner and want to open the car non-destructively, then your suggestion of not driving a dashcam and using a tesla probably isn't going to save you either.