Fortune did not "assume that Tesla had complete information from the moment this accident occurred." Fortune merely noted that there was a long period of time between the time of the accident and when the information was disclosed. Fortune is not saying that Tesla did have knowledge of what happened, it's saying that Tesla should have had knowledge. And Fortune is saying that Tesla should have investigated more quickly especially considering the impending stock sale. Perhaps they did not because Tesla feels as though the death is not "material." Musk's logic on whether the death was material is so convoluted it defies any sort of logical counterargument, and is ultimately for the courts to decide.
Regarding whether or not the accident was not an Autopilot failure, of course technically it appears that the truck should not have turned, but this is what happens in normal traffic. We do not design autonomous driving systems with the idea that nobody ever breaks driving rules or laws, rather we design them with the idea that every crazy situation that we can think of, and a lot that we cannot, are likely to happen and we should attempt to avoid or lessen the impact of a crash whenever possible. When Musk says that there is "no evidence to suggest that Autopilot was not operating as designed and as described to users," I seem to have missed the marketing material where they say that the features work only when other drivers follow traffic laws. It's one thing if a construction crane drops on top of the vehicle (cannot be reasonably avoided); it's another when a truck crosses in front of you (where we can take various evasive measures to lessen the impact of the crash even if we cannot entirely stop the crash from occurring, none of which were taken in this case).
Regarding vehicle accident statistics, as someone who worked in active safety for several years (i.e. systems like radar-based crash avoidance that did not trigger in this case), when we look at these numbers to make comparisons, the entire idea as of 2016 is that when we combine a human driver with a lot of electronic help, you are far safer than driving without that assistance or if the electronics were driving for you. But Musk only compares autopilot, which is only usable in certain scenarios, with the entirely of vehicular death information (which by the way, is largely much cheaper, older cars with worse safety systems that lead to more deaths). We know for a fact that autopilot lulls drivers into becoming distracted and doing other things, taking their eyes off the road, etc, because it does not enforce drivers to keep their hands on the steering wheel (See NYTimes report today). The simple, obvious fact of the matter is that a Tesla would be far safer if it were using all of its accident avoidance technology and required the driver to be engaged with the steering wheel. Yet it does not.
As someone with experience with this technology (though not at/with Tesla), I would greatly like to see them push a software update that requires you to have your hands on the wheel while autopilot is engaged. Saying that you should do so is not enough when the tools to enforce it are there. Is is clear and obvious that that would make the technology even safer. Yet rather than accept even the tiniest shred of responsibility, Tesla has entirely closed ranks and blamed everyone else. I, for one, am disappointed in Tesla as a whole and Elon Musk in particular.