From the article:
But after tickets sold, its best offering moved to a more expensive fare bucket, Mr. Ridley said. With Southwest pricing, it almost always pays to shop early. It's rare when Southwest cuts the prices on seats at the last minute.
This is completely incorrect. Southwest's fares more than 12 weeks ahead are virtually always higher than the sale fares available 8 to 12 weeks ahead. More than 12 weeks out the other airlines will often (usually?) have lower fares than Southwest. It is in the week before travel that Southwest's fares tend to undercut competitors.
The end of the fuel hedges made the biggest change in pricing, however.
We had already inferred that.