Even after self-driving is statistically safer, there will be accidents where a human could have done better.
I think "could have" is doing a lot of heavy lifting here and it's making the question seem more complicated than it is. You can't make decisions based on hindsight from specific examples. If, hypothetically, self driving cars are statistically safer, then they're safer, regardless of any specific anecdote that suggests otherwise.
Maybe I'm not grasping what you're saying?