Volume,
It is clear that we can not design aircraft for the combination of all possible events and conditions, but it should also be clear that we can not claim all events to be unrelated.
I agree with you completely. However, it remains true that the aircraft remains flyable without stalling in Alternate and Direct Laws, as other crews have demonstrated. So there remains an additive element to this.
Re your other points; the quote I made is from the certification requirements, not advice to pilots! The aim is indeed that the aircraft should 'tell you something'. Likewise, your point about artificial stall warning is correct; natural buffet is independent of air data and can be relied upon regardless of the state of the aircraft's systems. That's the beauty of it.
On a technicality, loss of data is not the only reason why an Airbus might revert from Normal Law. Loss of Normal Law doesn't
necessarily mean that your air data is bad.