This looks like false advertising.
Gary and Dave DID remain friends long enough to release some differences than what I've read here.
First, they introduced variable damage and dice in the Greyhawk Supplement.
Secondly, though it is possible the Cavalier and others would have eventually come along...I HIGHLY doubt they would have allowed Trolls and Goblins to be default options for playable races.
Sure, they had the rule where the DM could allow a player to play any thing...but I highly doubt that there would have been defaults of Goblins or Trolls as playable races...even as options included with official rules.
If I recall, years ago I stumbled upon S&W when it was first starting. At the time they made the classic mistake of thinking BX and BECMI were akin to the OD&D. I threw a fit. I sent (what was probably a very nasty letter and other items) to them about it. (they obviously changed from that to what they are now...but it appears their knowledge of what OD&D pertained of and was developing as, even after a few months to a few years is still lacking to the extreme).
It looks like nothing has changed (sure, they got the original message, but they still don't understand the mind of Gygax or Arneson or what they actually did...as per what was written here...they don't even realize that while Arneson and Gygax still worked together some pretty drastic changes occurred with supplements and the SR!).
I feel this phrase
it's White Box if Dave and Gary had remained friends and partners. It's a dream of how gaming would have evolved with the simplicity and elegance you remember it having, but brought into the 21st century. White Box Cyclopedia asks what would happen if we had rode nothing more than a d20 and a d6 into the same infinite well of adventure of the modern era? You'd get a complete fantasy roleplaying game we all loved, without the baggage of being "advanced." Remember those simple days? You had a few pages of rules, but somehow there was no limit to what you could do. That is the essence of White Box Cyclopedia.
Is absolutely false advertising and has no understanding of what OD&D actually contained by the time AD&D was coming out...and what actually was released by both Arneson and Gygax working together!
Does it sound interesting...sure...I'll admit their ideas sound interesting.
But the presumptuous statements they made here are really grating on my nerves to the point that I really can't stand the them. Probably the reason If I had to choose one I'd go with OSE over S&W anyday. OSE doesn't have the arrogance to claim such nonsense that I've heard like the claims on this one.
What's more, is that we KNOW how Gary's ideas evolved (As he was still playing well into the mid 00s. His game was right there for any who ever played it with him). There are probably a few that know how Areson's ideas went as well (I'm not one of those) though there were probably fewer of them, I think he still had his own game. He was also involved with Blackmoor (which I do have both versions from the 00s) though how much of it was guided by his personal attitudes and designs...I don't know.
I don't think these S&W guys have actually referred to those who played with Gygax and Arneson and how those games were actually run and what was actually available to them...AT ALL (though, I would be happily shown that I am wrong on this one).
They should remove that comment (which I quoted) for false advertising.