These guys may have it bass-ackwards.
What you're looking at is ENSO area 1, 2....the area right off South America at the equator; from a climate perspective, it doesn't matter that much (and as you can see, the cold water there has been displaced a bit north for the last couple of weeks.
What climatologists use to define El Nino and La Nina is the Enso 3.4 area..which is the area along the equator in the CENTRAL Pacific, not off South America. And you can see the SSTs there are below normal.