But that’s a sample size of one, so we can’t really draw any meaningful conclusions from that data. (Also the safety driver was watching Netflix on her phone; it could be argued that the vehicle was not production-ready and not expected or intended to be able to handle every situation.)

Let's say everyone replaced their current cars with self-driving vehicles and they never killed anyone ever again. If normal vehicle usage continued and fifty years passed without a single traffic death, your claim suggests we'd still be unable to say if self-driving cars were safer, as it would still be a sample size of one.

I don't think your use of statistics is correct.

I'm not sure that sample size is a relevant idea here, but it's certainly misleading as you state it. One accident in many billions of miles would be a wonderful result, but you would dismiss it as a sample size of one.

Is that data on self driving cars or assisted driving? I think disengagement statistics also need to be factored in.

That's the Uber "Level 3" accident.