If they do, I can't really see it as being more than a very limited sense. Otherwise, every setting gazetteer or the equivalent would count, which rather dilutes the meaning.Players guides count?
The Modiphius campaigns (Odyssey of the Dragon Lords, and Raiders of the Serpent Sea) have detailed player’s guides that really do session zero material well.I'm reading the new DMG and its section on session zero is good. Does anyone know of a published adventure (official or otherwise) that has detailed session zero material rather than "adventure hooks"?