The description at #1 re the 737, is ‘Crossover Speed’ - not AoA. This is the speed at which full opposite roll-control cannot maintain wings level flight with full rudder application due to failure.
A quick search for ‘A320 crossover speed’ did not find anything of help.
Because crossover speed is not a certification requirement it is unlikely that there have been specific tests. Although some manufacturers / authorities will investigate the situation as a qualitative assessment of aerodynamic response and control effectiveness.
The 737 issues involved accident investigation after rudder failure (
The 737 Rudder Story)
With much higher integrity control systems in modern aircraft it is unlikely that a failure situation will be encountered. However, there may be unlikely situations where the yaw input is generated by means; e.g. the un-noticed combination of having one engine at high thrust and the other at low thrust or failed, and the crew not using rudder.
A remote situation, and more interesting scenario as above, but with the AP engaged which reduces the available roll control.
Lateral control limiting with sideslip