Unless the BEA is simply being coservative and admitting that it's unknown.
... or just at a loss to explain the protracted failure to recognise inappropriate attitude?
The roll axis traces in the first half minute after AP disconnect suggest the PF was struggling to get hold in this period, with several regular cycles of overcontrol left/right.
I cannot envisage this happening unless he had a working display as reference ... too regular.
Proof positive - or not?