Yes, that's essentially the story. It misses a lot of safeguards that should have existed (from a hindsight is 20/20 perspective). There's no "fully trusted" in

Yes, that's essentially the story. It misses a lot of safeguards that should have existed (from a hindsight is 20/20 perspective). There's no "fully trusted" in safety critical code, so the software should have gone through a complete review when the safety model changed from hardware based to software based, including a HARA analysis and single point of failure analysis. The software should have had a specification and testing that included things like counter rollover and variable race conditions. The single developer should have had someone else to review their work and catch mistakes. This is standard practice these days, in large part specifically to prevent disasters like therac-25. While it's a little unfair to judge them by standards that didn't exist yet, it was still a broken process.