Although outdated (sorry!), there is discussion of co-terminals in the
Wiki FAQ. As noted there (specifically regarding PBI and FLL), the "Area" groupings are not the same as co-terminals. The Wiki FAQ points out other oddities, such as: why are SAN / SNA, AUS / SAT, and TPA / MCO
not co-terminals when other co-terminals are more widely separated?
When LGA and DCA joined the network, it was unclear ahead of time how those stations would be handled regarding co-terminal status.
A long time ago southwest.com did have a co-terminals list, but it was removed from the site.
The co-terminals list might restrict the flexibility of phone agents during IRROPS, but the list does
not restrict what airport agents can do for affected passengers.