"unless credible proof to the contrary exists not a single one of them ever happened"
Look up "apocryphal" - there's a reason I used that word.
That said, I've been a passenger in cars where the driver is clearly _NOT_ paying attention to the road ahead whilst on cruise control (rummaging around on the back seat, etc) and that was well before the advent of collision avoidance systems. On one occasion I needed to grab the wheel to prevent the car crashing off the road because the driver had apparently drifted off to sleep.
The reason stories like the Winnebago are believeable is because there really are people like that and everyone knows at least one person who would do it.