xcitation:-
IMHO they were not aware of the attitude/airspeed or dismissed it as being bogus. The fact that they nosed up and finally reduced thrust to idle is consistent with a perceived overspeed and nose dive attitude. I have not read any alternative hypothesis that makes sense despite interesting discussions about THS etc.
Inclined to agree that they may initially have interpreted the upset as a dive, xcitation; probably 'influenced' by the fact that (assuming that the altimeter was reading true) they'd have been losing height at about 10,000ft. per minute! But there's no guarantee that all (or even any) of the instruments were 'reading true'; especially in view of the 'cascade' of no less than 24 error messages, which among other things had caused both the autopilot and the autothrust to sign off.
And I'm afraid that you're just wrong about them continuing noseup inputs. IMO the BEA note is more notable for what it leaves out than what it puts in; but it does at least report the fact that, with more than 10,000 feet in hand, the PF did in fact 'do the right things,' reduce power, and apply nosedown stick:-
The altitude was then about 35,000 ft, the angle of attack exceeded 40 degrees and the vertical speed was about -10,000 ft/min. The airplane’s pitch attitude did not exceed 15 degrees and the engines’ N1’s were close to 100%. The airplane was subject to roll oscillations that sometimes reached 40 degrees. The PF made an input on the sidestick to the left and nose-up stops, which lasted about 30 seconds.
At 2 h 12 min 02, the PF said "I don’t have any more indications", and the PNF said "we have no valid indications". At that moment, the thrust levers were in the IDLE detent and the engines’ N1’s were at 55%. Around fifteen seconds later, the PF made pitch-down inputs. In the following moments, the angle of attack decreased, the speeds became valid again and the stall warning sounded again.
Further, I've seen it mentioned that the reason that the THS went to 'full up' in the first place may have been because it was responding to the earlier nose-up inputs. But that raises the question of why it didn't 'respond' in turn to the later nosedown inputs, but instead, again in the BEA's words,
'passed from 3 to 13 degrees nose-up in about 1 minute and remained in the latter position until the end of the flight'?