I am surprised to read this from you, Optional. Crawford and Perkins have said again and again in interviews that they regard the "default" setting of D&D as the multiverse. Really, D&D never had a default setting and I think people return to that term because of the decision to make a "default" setting of Greyhawk for 3rd edition D&D. As someone who lived through Basic, 1st edition, 2nd edition, and on to today, I can say that the emphasis of D&D & AD&D back in the 1980s was of a generic fantasy role-playing game that faciliated play in many different worlds. That was part of the appeal: Play in Hyboria, your own world, Blackmoor, Greyhawk, Middle Earth, whatever. Gygax certainly encouraged this in the AD&D
Dungeon Master's Guide.
3rd edition seemed to have established some of the language and concepts (the notion of a "0.5 edition," "default" setting, and other terms I read uncritically repeated here on ENWorld and in other forums) from which the game has migrated but to which others have not consented.
Per my post above, I enjoyed your article and thank you for it, but let's leave this idea of a "default" setting put aside. We can celebrate Oerth, Abeir-Toril, Krynn, Blackmoor, and many an other setting without recourse to it.
A final note, upon hearing that Greyhawk will be the example setting in the new book, I often have thought of Mike Mearls's comment years ago about how he wanted to see Greyhawk return, but he felt it was not handled correctly with the large campaign setting books and box set treatment it previously received á la the Forgotten Realms. I wonder if the kind of concise, collaborative model of Greyhawk that Perkins and Wyatt are proposing for the new
Dungeon Master's Guide is not a realization of Mearls's aspiration for Gygax's world?