A bit of both, I think. To do this is really hard. And requires some changes to how the car is made. Some of these lessons learned are presumably are being introduced into the Model Y, like the single-piece rear casting.

There's also a ton of engineering needed to go into how to make better robots.

Tesla also patented a wiring harness rigid enough to be robotically manipulated.

Indeed. That's another thing I was thinking of. Robots are terrible at manipulating floppy objects like wiring harnesses.