Isn't that scenario a bit far-fetched? ...
The scenario is not far-fetched because it has happened before. We aren't discussing a shaft failure, we drifted to discussing a particular gear failure inside the MGB. With this malfunction the #1 engine doesn't rapidly spin up, it is still governed at 107% N2 and under load driving the TR, but not the main rotor. The #2 engine is still driving the main rotor but not the TR. If you move the collective the TQ on both engines will respond accordingly, #2 engine because of the main rotor pitch change, and the #1 engine because of collective yaw coupling and the resulting TR pitch change. A pedal input will result in a change in TQ on #1 engine but not #2 engine. When DECU are involved which talk to each other to maintain constant N1 on both engines, when there are vastly different loads placed on each engine due to the MGB gear failure, then the discussion gets interesting. But, as I mentioned before, not normally practiced in the simulator unless the trainees are a whiz at everything else. However it is discussed in the class during systems review, particularly if the trainees are sleepy.