From my perspective (psychology qualified) the statement by the PF of "no valid indications" is significant. It strongly implies to me that he was sufficiently disoriented by invalid readings from SOME instruments to become incapable of distinguishing whether he had any useful information in front of him at all.
This reaction that 'it has all gone haywire' is lethal because it undermines the best (and often only) means you have to regain situational awareness, which is to work the data. This has been true since the days of doped fabric, and has led to a consistent litany of stalls and CFIT.
Complex modal fbw systems add the peculiar complication that the aircraft itself can, in a manner of speaking, lose situational awareness itself. Of course this is purely algorithmic, but can lead to 'assisting' the pilot in a task at odds with his actual intentions, or inhibiting a warning as a false alarm, despite the fact that given the current flight phase and circumstances such a warning is probably urgently appropriate.
That said, it looks like plain dumbness rather than a side-effect of complexity when a stall warning seems to activate whilst approaching stall but then to quit in full stall, only to trigger again upon attempted recovery.