Hi roulishollandais,
How could the crew and the Court know really how the system works?
They didn't know exactly how it works, because FCOM is not that detailed. However, the system did exactly as it says on the tin - by preventing a stall.
I don't know how close to the stall you, as a passenger on that flight, would want to be flown at below 50' radio, but please tell us - how much closer to the stall would you still have been happy?