The Airbus may be capable of more than the certification standards in that regard, but importantly it needs to be recognised that the trim system is a little different to conventional airliners and this needs to be acknowledged in training and certification.
Dozy, I'd bet the test pilots
never stalled the bus with full nose up trim. If so, that is not a certified condition. The only way the system would then be allowed to achieve that condition would be in some highly improbable one in a billion chance. But we definitely now know that the odds are much higher than one in a billion. I think this is an issue in the aircraft's certification that needs correction.
Now if EASA agrees, we can start fixing the problem.
Either test fly the aircraft with full nose up trim and declare it meets stall certification standards, or prevent the aircraft from autotrimming beyond the levels it was certified for.