Hyper-V.... That would be pretty close. But the stall was pretty mushy up at 37,000 feet so the passengers probably felt little, as did the flight crew on a turbulent night. The big clue should have been that display you depict ALONG WITH the altimeter dropping. Even without reliable airspeed, it should have indicated that the nose needs to go down to get the airplane flying again. The cockpit voice recorder transcripts will be telling. It will be interesting to see if the vernacular involved is about flying the airplane or system observations.