There is a "side stick indication display" on the PFD, however it is only active while on the ground, and disappears shortly after rotation during take-off.
It is disabled after take-off because this indicator was only designed for control check purposes (e.g., during pre-flight) and could be misleading during flight.
There is a "side stick priority" button either pilot can press to take over the flight control from the other pilot (and/or from the autopilot).
How was the captain supposed to understand the sidestick states and plane behavior, if he just entered the cockpit and the control state is not displayed?
How could he even have been *sure* which pilot had effective control of the stick if either pilot can take it over?
Yes, he could have observed and figured it out; but the whole issue of stress and fatigue is that it degrades cognitive performance up to a point where even trained individuals cannot reason well - which is why instruments and controls should be designed for clarity.
I see a design error here. Updating the controls by adding a composite sidestick display to one of the panels is a simple technical solution - but probably an instrument update would be tantamount to admitting liability and therefore legally impossible as an initiative for Airbus to take if not mandated.