I'm not sure/don't see how (and am having legitimate trouble following the conversation and objections, because of it) the two are being viewed as dichotomous?
I mean, yes, you can have a campaign world that is incredibly detailed and established...or you can have a "make it as you go along/start with the homebase village and create as you go." I get that. That's fine.
But how is the reality of the "both" not obvious? The players, even experienced players who have adventured in the same game world for a long time [IRL], are not ever going to know everything about a place. The DM needn't (nor, truly can ever) have every detail in place and immutable throughout the world. FR probably comes closest from any campaign world I've ever seen, but even there there are areas and details that do not officially (been put to paper) exist [yet]. Let alone the PCs!
There's a lot of conflation in these kinds of conversations of Player and Character, and the idea that if there's something in a book and the player reads it, then the character just automatically knows something. Separation of Player and Character knowledge (and the enforcement, by the DM, in game) seems/sounds like it is all but extinct. No character is going to know everything about any given world.
My homebrew world is...fairly well estabished. The continent's general shape and size, borders, areas of notice, persons of interest, geographical locations, locations of the major/known strongholds of the various races, racial/ethnic/cultural/historic tensions/rivalries, and general overarching plot possibilities are all in place...have been for a while.
But it isn't really until a party/characters are placed in their starting location (which will give them a degree of starting info) and they begin to roam/adventure/explore the world around them that any real understanding of what's around them/available in the world...let alone how the reality of what an area/region/kingdom is like vs. what they have heard/is common knowledge about it.
So the paradigm of play, from a character's perspective is [I maintain "should be"] always "starting from nothing/little and learning/creating more detail as they move out from there." And "details (both established and just ideas)" of the gaming world can be altered as needed or wanted as the characters encounter them. As long as a particular group's version of the game world remains consistent/intact (locations not changing, etc...) I can have as detailed a world as I want....doesn't mean a player or character or group of characters are all going to encounter/experience the world in that level/amount of detail...or that the detail might not change, over time, by location, depending on the player's curiosity and thoroughness.
Am I making sense? Or just rambling before having sufficient caffeine? It's tough to tell before coffee #2.
What I'm trying to say: a campaign world can [and I submit, the best "should"] be detailed while the reality of the characters (definitely) and players (possibly) still knowing very little/having a very small known window with more being filled in as you need, as you go.
I am not following how this is being discussed as a "A campaign world is/must exist as one or the other"...or, for that matter, what either approach has to do with shaping and enforcing a particular view of the world for the players through the use of "no."
If I say "No, there are no dragonborn on this world [because: detailed world creation sez no]."
OR
"No, in the valley/village/city/region/square mile where you guys are going to start the campaign and know about, no one has ever heard of/seen a dragonborn before. There's no reasonable way/reason such a character would/could exist there. But I haven't really thought out/detailed anything beyond that. Maybe we can introduce them later...maybe not...but they are definitely not here/available to start."
The answer is the same, make a non-dragonborn character.