Those settings were not used for educational purposes.
Maybe I have a higher standard of education
Maybe you have a wildly inappropriate one in this case. I mean, seriously. Your intended audience is…let’s see.
* Probably almost entirely over 40 or so, to be throughly familiar with any previous version of Greyhawk. There’ll be some (relatively speaking) kids in the mix, because some of us nerds are always going deep dives into history of times before our own, but not a large fraction. Mostly they’ll be people with their own memories of reading and maybe playing or running Greyhawk before.
* And yet apparently unfamiliar with the process of moving from one edition to another, because they need everything explained as if it were their first time.
* Given to poring over the entire contents of the DMG, and who will reading anything that mentions their setting in any way and apparently won’t or can’t say “this is for newcomers, not me”. Also, they expect a 32-page chapter to lay out an entirely world, history, and cosmos, and will be shattered if anything is left out.
* Or, alternatively, they’ve been reading D&D for 20+ years but have never built a setting of their own and feel the need of a primer, but will be shattered at any suggestion that one might create a setting of their own about like this but not embed in it layers of multiple previous editions the way the creationist Crestor stuck in fossils to present a false history.
You really think there’s a large enough population of such people to warrant giving them, and in practical terms only them, ten percent of the DMG? I just can’t.