This sort of thing happens frequently. Ding sales are planned far in advance. WGA special fares are often posted in response to competitors' sale fares, with the lower fare not being publicized by Southwest in any way. These are effectively semi-secret sales.

Would it be better if the Ding fare selections were more tightly coupled to the department managing real-time fares? Probably. But there are so many other ways in which Ding underachieves that I find it hard to complain about this one.