The problem is that a false positive causing emergency braking is also dangerous. So you'd be trading one instance of the car not emergency braking when it should against however many instances of it dangerously doing so when it shouldn't. That isn't an obvious call even before you consider that the human driver can cause the car to brake when it should but can't cause it to not break when it shouldn't.
The only real solution is to get the false positive rate down. Which is why they still have human drivers until they do.
The only real solution is to get the false positive rate down. Which is why they still have human drivers until they do.