To me the problem of AI is not how it works but how reliable it works. Do we have a way to test AI to prevent corner cases which could lead to catastrophic results?
How does the car deal with object X on the road? For X=piano, a stack of solar panels, a tank, an airplane, a pile of stones ...
No one knows and since the size of the set of X is infinite, no one can appropriately train for it either.
That's why we can't have self-driving cars without a general understanding of what objects are and how they move.