It doesn't seem at all clear to me that it was "spin" when there were cases of floor mats getting caught under the pedal, incidents of driver error, and physical problems.
It also is striking that the analysis could not provide an example of a single error condition that would cause the crash scenario. It's only a high level analysis.
It probably wasn't just spin -- Toyota probably didn't initially believe that they had a multiple-fatality software bug. When I first read some of the news stories about this, years ago, I also thought it sounded far-fetched that a bug that caused your car to accelerate to 100+ mph and crash could have made it all the way to production.
But it is important to note that the post we are all commenting on here isn't "the" analysis. This is just an academic case study of this now-infamous and interesting case, based on public information.
The closest thing that we have to "the" analysis on this (since we will never see Toyota's internal analyses) is, as tokenrove linked to elsewhere in this thread, the one Michael Barr did that was the main analysis[1][2][3] used in the court case against Toyota.
But there have been a lot of other interesting articles and posts on this case, other than just this one.
How hard would it be to get an old prius from a junk yard, extract the ECU, extract the software from there and reverse assemble and annotate the whole thing?
The hardest part I figure would be getting around the inevitable read protection but there are some folks that have done very interesting things in this arena (for instance, reading out pic chips that had their read fuses blown).
It also is striking that the analysis could not provide an example of a single error condition that would cause the crash scenario. It's only a high level analysis.