BOAC...
I cannot answer all your points... as ever, what is behind the Airbus is not told to us as pilots... after all, you cannot know each software line.
However, before you say "I told you so", in fact some of the logic seems more robust than I had understood (which is not necessarily a reflection on groundschool or manuals!).
Stall Warning: Conventional understanding of the Stall Warning was that this could not occur in "Normal Law". It now seems that it is not "inhibited" in Normal Law, just the "Normal Law" protections should "act" (prevent you increasing AoA) to the extent the "Stall" warning is never triggered. What happened here was that High AoA protections, which the purpose of the test was to check, did not occur due to the frozen AoA values. The "Stall" wanring therefore did then get triggered, as they slowed, by the remaining AoA probe. So there is a "backup" to the AoA protection.
Is 99kts a realistic speed for a stall warning at that weight?
No idea... But my understanding of the report is it probably is OK.
is it not sensible to ask a system to make it clear that what systems you thought you had were obviously not in fact there - a fact really made clear only to the aircraft?
In the Test case, the Test Schedule gave the speed at which the "protections" should occur, and the test was to ensure they occured at that speed. This is not a "slow the aircraft until it goes bong" test, it is slowing it towards a **** great red tape on the speed scale. Therefore you half know the result of the test before you get there - if Alpha Max is shown as 110K, and the table says 111K, you have a pretty good idea all seems OK. If in this case, they are 20K+ different (cannot recall the numbers), you know even before you get to the speed you have a problem. This is the crux of the test - test protocol would anticipate the result and not sail 10K..20K below it going "errrr???"
I would wager that an average crew, given this information, might not rely on them
To an average crew, in Line Ops, the only time they should get anywhere near these AoA limits is in a "GPWS Pull Up", or possibly a "Windshear Go Around". The rest of the time we fly like your B machine - to speeds that unless you get grossly below keep you well clear of the stall/protections... although a crew should be familiar by experience at those red tape(s) sitting somewhat below the App Speed.
This is not just about a rare event caused by incorrect washing. This goes to the heart of a system which encourages absolute confidence in Msr Ziegler's concierge's undoubted ability and then 'blows a raspberry' at the poor crew.
As you might expect, I would not agree 100%
The incorrect washing was but 1 factor. I am 99% sure that if the next sectors were flown by a Line Crew, there would have been no incidents, probably some PFR/Status/Engineering messages, and a moderately sharp crew would have queried the speed scales.
As ever, the tragic outcome took an exceptional event (2 AoA sensors abused by washing), poor approach to the testing (understanding what and why you were doing and no Plan B), poor decisons on the day (do at 10000' below the min stated Alt), and bad luck all the above got combined on the same day
I personally have learned some AB characterstics from this accident, good and bad, but see no need for a substantial change in design or SOPs or training. Some will no doubt disagree - however, the report largely does agree with my pov.
You quote some lovely Airbus folklore above - I think that largely got disspelled at Habsheim and Strasbourg. As with any aircraft, it has it's good points, it's bad points. The "protections" are rarely used - any SESMA / QAR monitor man will be after well before you get there
NoD