It will be interesting to see if the substantial safety margin decreases as more people buy in.

I do know that there is not much better than average driver! There is much worse than average: people who drive drunk, and a few other classes of people who shouldn't drive at all. However the vast majority are all about equal: in reasonable mental health and limited to the same eye and reaction times. A few people have and follow better training and so are slightly safer - but this is slight. Most people think they are better than average because they excuse their mistakes as a "one time mistake", while confusing "the other guy's" mistakes with the other guy must be a bad driver.