The situation is slightly contrived, but one which reappears in some LoC accidents.
The flight test aspect was many years go involving validation of FAR/JAR for the Russian Federation acting on behalf of a third party.
Their special conditions required evaluation of situations which had previously resulted in accidents, more of interest than requirement. The particular situation related to likely LoC; cf, a Russian operator, and similar to the 747 ‘roll-over’ in the Pacific.
My ‘no rudder’ restriction was chosen to limit any emotive debate of why the crew did not use rudder (or understand the situation), this also enables the situation to be considered more widely and compared with other types.
The test aircraft, Avro RJ, like most others, could achieve and maintain the unbalanced condition with manual control. However, the test point was difficult to set up, requiring co-ordination between yaw (significant thrust split) and applying aileron - need to start with aileron, but yaw had triggered the event. Misjudgement led to disorientating roll-yaw over-bank, and surprise that the situation was not as expected. Typically once the balance was understood the task was easy; a stable condition was achieved and the aircraft could be manoeuvred.
In intervening years, aspects of expectation / disorientation had been identified in 146/RJ autopilot upset incidents, also in accidents with other aircraft types.
The autopilot aspect is a practical starting point; yaw asymmetry (un-alerted thrust split) results in roll, but the AP limited control, and probable disengagement, directs pilot attention to roll and AP failure.
Thence with increasing roll, even if the aircraft is capable of manual recovery, the disorientation, need of instant maximum aileron input, which with continuing yaw might result in an unrecovered LoC accident.
The human aspects involve judging the human contribution in assessing the dynamic situation and then choosing a suitable course of action to recover control. If the pilot gets behind the control requirement - less than full aileron, unaware of thrust split, and with increasing roll, the situation may not be recovered.
Seeking an exchange of views and experiences.