I can see no reasonable means of engineering a system which would "reposition" the THS as a result of being in a detected "stall".
The whole point of being in a degraded mode with reduced or no envelope protection is that the system can no longer rely on one of its primary protection inputs - alpha.
if, despite that lack of reliability in alpha the system were, in a degraded mode, to have authority to move the most power single surface on the aircraft through close to full authority ( NU to neutral is a LONG way) it would be utterly impossible to show the system as being safe - in the event of an erroneous AOA input, you'd still be exposed to a large stab runaway, in effect.
With the AOA reliability suspect, the system can no longer act, automatically, on AOA. All it can do is draw the attention of the crew to the apparent high AOA situation - shake, shake - and hope they, with their human reasoning and airmanship, can resolve the situation which is outside the design parameters of the FBW system.
Unfortunately, in this case, they couldn't or didn't.