When the right engine went to auto-feather, would there not be pronounced yaw to the right, resulting in left rudder input, and a dead-foot/dead engine clue to guide correct identification and shutdown?
Auto-feather can cause a momentary yaw into the operating engine as the prop goes into coarse pitch. After that transient impulse has passed the rudder input required to maintain longitudinal trim leaves no question as to which engine is still developing power.