From the report
While intervening, the co-pilot had not pressed the take-over pushbutton, therefore both pilots’ control inputs were added and averaged. Such dual piloting is prohibited by the A320 FCOM. At that time the actions of the two pilots were not coordinated. The Captain twice moved the side stick half-way backwards , possibly, reacting to the EGPWS, but at the same time the co-pilot was inadvertently making nose-down inputs, which might have led the Captain to believe that the aircraft response to the control inputs in the pitch channel was not adequate.
My bolding. Without a A v B argument developing would the Bus drivers care to comment on this aspect. Is it an area/scenario you cover in the sim (Train like you expect to fight, fight as you have trained)? Man/machine interface aspects?
I realise they were likely not following procedure (co-ordinating their efforts) here as well, but I ponder the reason why the copilot failed to press the button if he realised things were going pear shaped..