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"?
Is this what was meant by "player's guides"?You'll have to define what "Session 0" would mean to you.
Otherwise, I consider "player's guides" to be the closest thing, and I make one for every campaign I run, such as my Dragonlance Campaign Guide. It's got everything a player would need about the setting and making a character linked to the setting.
This habit is largely inspired by Pathfinder adventure paths, each which has a free Player's Guide with unique backgrounds and mini-feats to link folks into the campaign, stuff that differentiates it from another campaign. You don't have to pick between 3 bullet point generic ideas to start your adventure. The adventure is already started. See Kingmaker's Guide.
See also a Dark Sun series of free adventures (that I've been helping edit). The first adventure provides backgrounds (with rewards) to hook characters into why they're headed to this particular village. It's not a full-blown guide and is designed to let folks more immediately jump into the adventure.
Is this what was meant by "player's guides"?
Because I was expecting things like Player's Guide to Faerun (a 3.5e text) or Eberron Player's Guide (4e text), neither of which is particularly good for the kind of purpose you describe here. They're more like...the whole text? Like they describe EVERYTHING about the world, not a quick, focused presentation + hooks to get folks ready.