Inexplixable Happens
An acquaintance of mine was once making a routine test flight in a helicopter under development. In the brief, he had been reminded by engineering that high-inertia rotor blades were installed (not part of the test) and therefore not to let the rotor rpm get too high. During the flight, which involved shutting down an engine, he was presented with an unanticipated failure/condition with the rotor tachometer going to and freezing at an overspeed indication. He raised the collective to get the rpm down and fixated on the indicated rpm. He persisted in holding the collective up even though it wasn't producing a change in the indicated rpm and the rotor had slowed well beyond the point that he should have first recognized that it was below normal. (Apocryphally, to the point where he should have been able to see the individual blades instead of a disc...)
Presumably Airbus and Air France are putting line pilots into a simulator and exposing them to the same instrument indications and aural warnings to see what they do.
My understanding is that the side sticks are not connected and have limited range of motion so the pilot not flying and the pilot(s) observing have no idea what the control inputs of the pilot flying are. If the pilot flying were doing the inexplicable, they wouldn't be able to tell?