Well, dwarfs have been in GH since it started, but goliaths are new. Dwarfs have several established kingdoms in GH, but goliaths don't. Dwarfs have had large amounts of text dedicated to explaining their culture, both in and out of GH-specific material, but goliaths haven't.
So there's three reasons why goliaths would be a problem.
Elves also have existed, have kingdoms and have large amounts of non-5e text dedicated to them. But in the post I was quoting you presented the challenges of Goliaths and Elves equally. After all, non-5e material doesn't count right? To teach someone they will have to present the dwarf lore as though they were new, because someone with no expeirence with Greyhawk and no expeirence worldbuilding, who is new to DnD as of 5e has no idea what kingdoms are in Greyhawk, or about their history.
So, by your own standards, there is no difference between them. Except we can count the 2e and 3e Dwarf Greyhawk material for some reason even if it isn't in the book, and we cannot count the 3e Goliath material... which is sounding like a double standard just because Goliaths used to be outside of the PHB and therefore no one cared about their established lore.
Good thing I said "sentence or two" and not "paragraph, right?
I will state that even a novice worldbuilder should be able to manage one sentence on each of their PC species. Assuming that the worldbuilder is going for the D&D standard of each species being a distinct people with their own language and distinct culture, that is.
It wouldn't even be difficult. The DMG could present a few questions to be answered, such as "how do they feel about outsiders/people of different species?" with a few examples given such as "welcoming,""friendly but cautious," "wary and distrustful, but willing to keep the peace until provoked," "usually hostile at the get-go," or "demands they prove themselves through trials." There could even be a table to roll on or choose from, or to use as examples should the DM want to make up their own answers.
A paragraph is 4 to 5 sentences. IF you have three questions for each race, and each question takes one to two sentences... you have 4 to 6 sentences.... which is a paragraph. You can't talk about ecology, government, species relations, and history all in a single sentence. Not if you want to have answers that can be used.
You are once again confusing worldbuilding with actual play. And funnily enough, you're actually making my point, except that because of that confusion you think you're not.
The writing in the world book or chapter or whatever--the book that WotC will be producing--will be showing how the Orc Empire is not evil (again, "not chaotic evil" does not have to mean "always good"; the orcs can be neutral). The DM will then, hopefully, show this in their own campaign by having the PCs interact with not CE orcs and orc societies.
Worldbuilding isn't telling because it's a different form of media from the actual play. It's a literary media, and more specifically, it's (usually) a wikipedia-esque listing of facts. If the entry on the Pomarj claims that it's not an evil empire, but there's nothing to support that in the text, then it gets a big fat <citation needed>.
Oh, world-building is a encyclopedic listing of facts. In written form. Like I keep saying.
Here, do me a favor. Look up the meaning of Show don't Tell. It is a writing rule, for the written word, that talks about not simply telling people things, like listing facts. Like a wikipedia-eqgue listing of facts. Like the literal thing you keep claiming that world-building IS.
Also, world-building is not a media. It is an action. There is an action verb there, "building". World-building is the act of building a world. This can be done through a characters actions (which would be SHOWING) or it can be done by listing facts of the world. Which is TELLING. The type of world-building we are talking about, which is making a reference document, is entirely TELLING, no showing. Yes, even if you tell people about actions of characters to reinforce an idea of "goodness" it is still telling. That is literally why people engage in telling so much, to tell people facts that support the idea they want. Which is why Show Don't Tell became a thing.
Were a lot of people upset when Nentir Vale was introduced? I admit that I wasn't paying attention to anything D&D during the 4e years, but the reactions I've seen to it have been between "high praise" and "it's OK," with most being towards the "praise" end of the scale.
Would a lot of people be upset if this world was created for the sole purpose of being used as an example of how to build a world and wasn't actually turned into a real setting? I don't think anyone here is saying that this hypothetical world must be used as a new setting--just that it would be a good idea.
Hard to tell if anyone was specifically upset about Nentir Vale, since they generally hated 4e as a whole. Couldn't tell you if anyone only hated the new setting, but I will guarantee MANY people complained about it.
And why would you waste time and resources on a setting that is never going to become real?
As for no one saying it must be a new setting, sure, but you also refuse to acknowledge there is literally any benefit at all to using Greyhawk, which is what is keeping this conversation churning. You are convinced that this chapter, which is likely already written and being finalized, is going to be horrible and without purpose, solely because they picked Greyhawk and if they had just decided to make a new setting instead, it would be wonderful and perfect.