> the strong likelihood that two different ENSO dipole mechanisms may be at play.

The different flavours of El Ninos must imply some difference in mechanisms. Separating them out also seems to me to be a sensible move.

Watching the currents and temperatures on earth.nullschool.net over the winter this year's El Nino seems to have a very anomalous path to higher latitudes dumping lots of hot water off the Californian coast; I've never seen a description of any previous one showing such behaviour.