Flying with Rudder, Elevator, Throttle (no ailerons)

I set up a small plane with rudder, elevator and throttle controls only - no ailerons. I put the rudder servo on the aileron channel.

The plane flies well and the flight controller works fine in AUTO mode.

I just noticed that there is a parameter for rudder only operation: RUDDER_ONLY mode.

What is the advantage of using the rudder only set up in ArduPlane?