When I used to conduct full flight tests on 4-engined aircraft, there was a strict 'Test Schedule' which defined height, speed, weight and requirement for every stage of the test.
Tests were only conducted by one of two appointed captains for each variant of the aircraft as the tests were infrequent, but demanding and it was vital that we had to be very experienced on type. New full flight test captains would first practise the entire test schedule in the simulator.
We flew with a crew we'd selected, including a highly experienced test co-ordinator who 'read the script', although I had my own 'cheat sheet' to remind me what the next test would be. We took the aircraft from over M0.9 down to stall warning, but only in accordance with the schedule and in clear airspace with no ATC interruption.
So to conduct the test in the way they did seems to violate all normal rules of flight testing. Time pressure (delayed take-off), commercial pressure and ATC pressure combined with an ad hoc approach to the test and you have a recipe for disaster.
Test points are defined for a reason; flight test pilots may not know the reason, but must stick to the test points. Rigidly. No great 'golden gloves' handling skills should be necessary for engineering flight tests (as opposed to prototype testing), but a disciplined approach to such flying is absolutely essential.
Although I have no experience of the A320 series, the aircraft clearly has a sophisticated flight control system. Forcing the aircraft into any specific law should obviously not be a routine event and if a test specifically requires 'alternate' or 'direct' law, there must surely be a specific procedure to follow?
I can't think of a much worse scenario for the conduct of a high alpha test then the scenario of this accident.
Incidentally 'Manual
Trim' is slightly misleading when the tailplane angle is such that it is outside the elevator's authority to control pitch - if the tailplane angle is such that full sidestick cannot correct the aircraft attitude then the 'Manual Trim' becomes the primary pitch control until the tailplane angle is within the range for the associated speed where attitude can be controlled by elevator.
The lack of THS movement in 'direct' law in this accident is highly significant - perhaps more so than the allegedly unserviceable AoA probe(s).