Appears he was reducing back pressure at the stall warning and then immediately (and excessively) increasing it, or possibly he never reduced back pressure and the plane was just oscillating in the stall. Either way I'm not sure this supports your position. Training with an AOA indicator may have helped him understand how to max perform his aircraft without exceeding the critical angle, and may even have helped him predict the limits of what he could do with his flightpath so he could choose an earlier/better alternative path. The stall warning is just an on/off indicator, while the AOA gauge can give a progressive indication of AOA. This pilot's decision to continue up the mountain severely limited his options and put him in a square corner. If any gauge could have helped him at the end game, it would have been an AOA.