I agree with you that Wildemount should count.
To be entirely fair to WotC, even Keith Baker would defend the enormous input Bill Slavicsek and others at WotC had in the creation of that world.
Keith may be the parent and ongoing steward of the world, but it wouldn't be Eberron without WotC's R&D working with Keith to turn it from a one-page pitch "Thrilling Tales of Swords and Sorcery" into the expansive world it is today.*
You can hear it from the horse's mouth below:
The Origins of Eberron: Bill Slavicsek
Ultimately Eberron was a collaboration between WotC and Keith, while Exandria is a world created by Matt Mercer that has been adopted by WotC. WotC certainly gave input into the mechanical crunch in the Wildemount book, but the Exandria world details were from Matt's home & streaming campaigns. Eberron didn't emerge the same way as say, Greyhawk or Mystara. It was developed and workshopped for the sake of selling 3.5e, not for the sake of being someone's private game world that spread by word of mouth (or streaming video channels, per Exandria).
*I say 1 page pitch, though it did become a 10-page revised pitch before working with Bill to refine it into a 100-page story bible. And even then, that story bible was far from what we know today as Eberron. A LOT went on in developing it once Keith got to Seattle and got to sit down with Bill, and James, and Chris.