You are reversing the meaning of nines. It is a guarantee of performance, not a guarantee of failure. 99.999% guarantees all but 5.26 minutes worth of a year's (continuous, non-stop) driving. Those remaining 5.26 minutes might be fine, but they are not guaranteed.
Flip it around, how many minutes is a typical driver "guaranteeing"? That is, what is the average failure rate for a human driver. If Tesla can really achieve five nines (which I doubt, except for limiting the circumstances) five nines is almost certainly better than any human driver.
I don't have the data to back it up, but if someone drove 60 hours a week, fifty weeks a year do you really think they would only make 1.8 minutes worth of mistakes? I think a reasonable person can accept that human drivers make errors far more frequently than that. The question is, when will Tesla be able to demonstrate 99.999% performance?
[edited to make more evident the part I was responding to in the quote]