I like your style with the video presentation 
Your two points with regards to the back-flip and the vibration also caught my attention when comparing the dam video with yours. However I believe the disparity can be explained by how much power was being delivered to the props at the time of failure. From your video I would say you were moving at considerable speed, unlike the guy at the dam who was more or less hovering. A sudden loss of lift at high thrust could overwhelm the stabilisation - enough to tip beyond 90 degrees. As for the vibration, there are many factors as to why it would be in or out of phase with the EIS: the video frame rate, the final speed of the props, the stiffness of the arm hinges?
I am also trying to claim warranty on a lost Anafi from what I suspect is exploding propellers. If your incident is related to prop failure under normal usage, and the fact that your props have only seen 4 hours of flight time (and assuming no collision with a very hard insect) then this scenario would be unacceptable in my books, and definitely outside of operator error.
