This is the main problem with "auto-driving" features right now. They work well enough that the driver stops paying attention to the road, but not well enough to be 100% accident free. This allows the auto manufacturers to point to distracted drivers as the cause.
We probably need something like an insurance fund paid for by the makers of the technology to handle the claims that come in. It would force the manufacturers to be a lot more cautious of rolling out these features.
I tried it once, the car started beeping, then louder, louder, much louder, then started quickly biting the brakes in short intervals. After that I decided that I should let the car know I'm still alive.
But it should then put on the blinkers and slowly come to a stop.