This damn "we" and "them" is not productive to accident imvestigation and how it is suppose to work.
Of course it needs to be a team approach with the same objectives of preventing the next accident, rather than finding fault or protecting someones reprutation.
All investigators know this (wherever their institution), but those on the sidelines continue with their presumptions of guilt.
Sure Boeing and the NTSB investigators (add others at will) make mistakes in assumptions and investigative findings, but not from a devious plan to obfuscate, We leave that to press releases
It's easy to say that it would have taken 4 separate combinations of faults for such and such to happen. After all, that assumption was already verified in the product certification. The objective of the accident investigation was to find "How' and then "why" followed by the lesson learned. From my viewpoint the only criticism would be that an investigation didn't meet that objective.