I'll admit i didn't read all of either document, but I'm not convinced of the argument that one cannot attribute a failure to a root cause simply because the system is complex and required multiple points of failure to fail catastrophically.

One could make a similar argument in sports that no one person ever scores a point because they are only put into scoring position by a complex series of actions which preceded the actual point. I think that's technically true but practically useless. It's good to have a wide perspective of an issue but I see nothing wrong with identifying the crux of a failure like this one.