At long last I believe we are closing in on what may be a lay solution. As such, it is of little value, save for some sort of truce. It also may be as close to a resolution as anyone gets, including BEA.
2:10:04.7. A/P quits. Here, the Nose is 4.5 degrees lower than what it should be. With MASTER CAUTION and CAVALRY CHARGE, the PF is brought up short, from whatever his status was, re: SA. A quick glance at PFD, if not already looking, shows NOSE LOW, and VS in descent, perhaps 500fpm. 2:10:07, and he inputs back stick with a ROLL LEFT.
The a/c has started to climb at a/p quit, and there is not a reason to doubt his input causes sufficient NOSE UP to trigger STALLSTALL. His next inputs are NOSE DOWN, so he 'gets it'. The rest depends on what he sees on his screen, feels, (The g is <1 until after his input), and decides. (Hears?).
If there is mitigating data, sufficient to establish his inputs were based on data not seen here, I propose there is a 50/50 we will never see it. That is the way of the world; life is harsh, and seldom "fair".
At long last the discussion is where it should have been from the outset.
With NOSE DOWN, I would submit that it takes a healthy Updraft to cause such an ascent as we see just prior to a/p loss. Was it sufficient to cause the accident? Was there ICE? or only variable TEMPS and a bumpy airmass?
It's been a real slice.