I don't have experience with self-driving cars, Uber or Volvo safety systems, but my Jeep's backup collision prevention often slams the brakes if I'm backing up and the camera detects potholes, oil stains, or irregular painted lines in the parking lot.

If any of the systems are vulnerable to any such false positives, and equipped to enable emergency braking to avoid them, even on the highway, it's not hard to imagine why they might be disabled, especially during testing phases.

I think it's fair to say that at this early stage in product development, there's probably no 'always right' answer for how to handle a given obstacle without considering locality, driving speed, road conditions, likelihood of false positives and negatives, etc.