"The captain needed the co-pilot to assist by pushing his control forward to make the aircraft pitch down." Correct me if I'm wrong, but I do not believe that the A320 requires forward sidestick on both sides in order to obtain a maximum nose down command. If the captain had full nose down input on his side, no amount of input on the F/o's side would make any difference. The captain didn't need the F/o to assist as asserted in the article & if he felt he did, it shows an extreme lack of understanding of the aircraft systems & of the principles of multi-crew operations.
Oakape, I suggest something has got lost in translation in the report. My understanding was that the FO was PF and in response to the autopilot disengagement he had full back stick as he was unaware the aircraft had dropped out of normal law with its stall protection. The captain was more aware of what was happening and initially told the FO to "pull down". This certainly got lost in interpretation as the FO continued to apply back pressure on the side-stick. The captain then applied forward pressure but without using his command button all that did was counter the FO's input so nothing happened.
Certainly it could be argued that he should have taken control by telling the FO to #@z*^\ well let go, but he didn't and the rest is history.