Hope this will clear things up!
View attachment 365173
When you get
this, then maybe we can discuss other things.
When I get what?
People who are long time fans of greyhawk exist, yes. They are not the target audience for a chapter on how to world-build. Sure, they may be excited about the inclusion of Greyhawk in the DMG, but the teaching aspect isn't for them. They are long-time fans of an established setting. Not new people coming how to learn how to build a setting.
People who know Tolkien tropes... again, they exist, but so what? Cultural osmosis will have told them Orcs are big, green and tribal. Which is nothing like Tolkien, but that's how orcs have been depicted since Warcraft redefined them. Elves? Other than being long-lived are elves magic addicts clinging to their noble glory? Violent xenophobes who eat humans? There are truly hundreds of different takes on "elf"... and most of them INCLUDING TOLKIEN do not apply to DnDn elves at all.
So two of your circles are nonsensical to consider, since they are mostly "long time fans of the setting" or "people who have read fantasy".
Your last circle is the closest to the actual audience being considered. People who are looking to be taught how to world-build. And, if you notice, that little purple part where you keep pointing to as a problem... is a tiny tiny sliver of that population, requiring that they ALSO be fans of greyhawk and ALSO conform to Tolkien lore, but not understand that Tolkien lore is different than DnD lore.
So again, how is this an issue, if there is a slim possibility that some small section of die hard fans who don't realize the game and fantasy have evolved over the last 40 years, might be upset that things have changed? They are a small part of the audience, and even then, half of them at least won't accept any changes, declaring that WotC is just dumb and stupid and doesn't know what REAL Greyhawk fans want.