Wow... I can't quite reconcile how AP2 cars were shipped without auto headlights and auto screen dimming... or side collision, for that matter. They still have ultrasonics, right? I guess if they're merging that data with the side cameras, sure, but fall back on just the sensors otherwise.
But the headlights/dimming... that's basically as simple as reading the lux value from whatever sensor (but again, I guess maybe they're using the AP camera...)
I also didn't understand how they shipped AP2 cars without even BASIC cruise control. That just seems crazy to me!
(1) They are confirmed to not have the previous ambient light sensor and rain sensor module that was on pre-AP2 cars. So they are indeed using the new Tesla Vision system for brightness measurement and rain detection.
(2) They have new ultrasonic sensors, which presumably behave differently enough from the old ones that they need to validate that it behaves well in real world situations like driving through tunnels / near overgrown landscaping, nearby other cars with ultrasonics, etc etc etc.
(3) Basic cruise control is extremely dangerous to offer on cars with TACC/ACC/semi-autonomous features, because it leads to driver error and misunderstanding (e.g. accidents where a driver was expecting the car to have TACC but it just simply plows into traffic). You can imagine how an existing Tesla owner checking out a loaner AP2 or a new owner who misunderstood and thought the car had AP/TACC could be lured to make a muscle-memory mistake like this.