Additional tests I did show that there's no sensor in the bottom lip of the rear hatch or near the spoiler, so anything interfering with those parts in their opening arc will be hit. The FWD roof sensor IS setting a opening limit for the hatch, but since it is several feet forward of the spoiler (and hatch lip), it doesn't actually detect obstacles these parts may hit. Protruding hinges on a roll-up garage won't be detected, just the flat planar surface of the overhead door. So,... be careful. If you set the hatch to fully-open outside, and then open it under your garage door, be prepared to stop the hatch on the first live test. Of course, stopping 3" short doesn't give you much reaction time. Maybe 3" of padding on the spoiler might be a good way to prevent damage if it doesn't work as expected.
It works fine for me, and allows full opening outside as well as restricted opening under the garage door. A nice feature. Since I now depend on it, let's hope Tesla SW engineers won't remove it in future updates without warning.
Now the question comes up: do the sensors in the rear bumper in any way prevent the hatch from opening into a rearward obstruction such as a wall or a closed garage door? At least the sensors did not detect my body standing directly behind the car within the arc of the opening hatch: it plowed right into me and kept going.
