Its not the NHTSA that's glacially paced. It's the simple fact that at current accident rates, statements about safety after one year of a model being on the road are statistically unfounded. It's simply not physically possible to say "this car is safer than average", because on average you would expect less than one fatality. Having zero fatalities in the first one or two or even five years after launch proves nothing.
Saying "our AI avoided four potentially-fatal accidents" is also a vacuous statement, since a) you don't know whether an accident would be fatal or not, since accidents are ridiculously chaotic systems and b) there is no way to say that a human driver would not also have avoided all those accidents.
In fact, most accidents are caused by people driving under the influence of alcohol or drugs, or falling asleep, or being on their phones. Using AI to detect and deny these people from driving would be orders of magnitude easier than autonomous cars, and provide 95% of the potential safety increase with none of the drawbacks. Why don't we do that? Consumer backlash is the answer. Even alcohol-preventing locks, mature tech today, is not being made mandatory because consumers would be mad.
I agree that brand reputation matters a lot. But people think we are going to see huge paradigm shifts in autonomous driving over the next ten years, and then your track record is for something completely different. Meanwhile the Tacoma is just a slight update and restyling of mature technology.
Adding to this is the fact that one freak accident will completely shatter a company's records. Imagine if a Tesla with next-gen Autopilot filled with seven passengers is driving through the Alps in October at 2°C: while the car is inside a tunnel, subcooled rain starts falling, covering the road in an invisible layer of super slippery ice. (This actually happens). The car goes off a cliff and kills all seven. Yes it's far-fetched, sure. But it will still be seven fatalities caused while the AI was driving, and that suddenly puts the AI car on par with a 2002 Honda Civic.