I agree. But my question is whether the decision to continue a 3 out of 4 aircraft is made oblivious to whether their are suitable diversion airports along the flight path, or whether this decision would be sensitive to this issue.
To me it would seem necessary that this be an important consideration. After all, with ETOPS, diversion fields must be within certain minimum distances/times. Given that a 2 out of 4 will be in a clear emergency, it would seem that if you only have 3 operating, you wouldn't ever want to be too far away from a diversion field.