Try replacing "acting unexpectedly" in your thought process (which superficially I agree with) with the words "acting safely."
It remains to be seen if autonomous driving systems are actually safe. But if the other driver does something that is safe, there's then an onus on the first driver to have accounted for that.
It remains to be seen if autonomous driving systems are actually safe. But if the other driver does something that is safe, there's then an onus on the first driver to have accounted for that.