They didn't mean the backdoor was (or was not) an accident. They meant the backdoor was implemented sloppily enough to be discovered and maybe that was not an accident (as in, he wanted it to be found, but still wanted to plausibly be seen as trying his best to keep those coercing him appeased)
I call that following the same successful recipe that got us the Falcon 9.
The mindset that considers those tests failures is the same one that would still be in bureaucracy hell determining what 40 year old technology we should repurpose to get a future over budget, late, and under performing solution designed and built.