Good explanation of the underlying problem. You’re dead on.
In arguments with other developers I’ve tended to attack it from a coding perspective, such as, “how would the algorithm handle driving down a road with no stripes?”
“If a driver in the left lane needs to get into the right lane by merging between 2 autonomous cars, will they kindly let him in by slowing down / splitting the distance? And what if there’s a semi behind the 2nd autonomous car, wherein a human driver would say, ‘tough luck’ and not let the driver change lanes?”
You can come up with countless examples of “judgement” vs. “functionality”.
What proponents of autonomous vehicles don't realize is that the only way to safely replace human judgement is to add such large margins of safety that the system you're automating is actually less efficient in an automated state than it was in its "human" state.
In the example you used, the merging process wouldn't be a problem because that two autonomous vehicles would be traveling about half a mile apart ... at a speed of about 25 mph. I'm only half kidding about that.
I have a real world example of the no stripes question. My wife’s Toyota Rav4 has radar controlled cruise control. In situations where the fog line is not continued through an exit ramp her car will decelerate along with the exiting car.