OK, let me simplify it for you. You're flying a MU-2, a twin engine turboprop. The right engine is critical, so let's say that engine is going to be the one to fail. Let's say the fuel control unit (FCU) fails such that it sends a • ton of fuel into the right engine. The engine starts to run in an overspeed, overtorque and overtemp condition. It's only a matter of time until the right engine fails. With the right engine running overspeed, the airplane will yaw to the left. Since the airplane is yawing uncontrolably, you suspect an engine failure. You are correcting for the yaw by using a lot of right rudder. Your left foot is the dead foot so you decide to verify by closing the left throttle (old piston habit). Depending on the phase of flight, you may be out of control already. I'm not sure because I am not an MU-2 pilot. Let's say the airplane stays under control. It will still have power because the right engine is still working for the moment, and because of this you will suspect the left engine has failed so you shut it down and it make it go to feather.
So now your good left engine is shut down and feathered, and it it only a matter of time until your right engine fails and you're screwed, wondering what best glide is in an MU-2 if you were lucky enough to keep it under control in the first place.
Mike