I didn't assume. I came to a conclusion based upon the data available. The key was that you included AD&D Greyhawk, specifically, which may not literally share 99% of monsters, but does share most of its iconic critters with later editions.
Since your point failed there in the spirit of the statement, there was a choice - conclude that you were outright wrong, or conclude that you were technically correct, but literal. Would you prefer I'd taken it the other way?
I truly don't see how my point failed in the spirit of the statement. You are saying Greyhawk shares most of its iconic critters with later editions; yet that is only true because many later settings borrowed from Greyhawk. The relationship is not reciprocal, except in the case of the Forgotten Realms, meaning that Greyhawkian D&D is thus the only D&D.
I will grant Mercurius's clarification that he meant all versions of D&D share 1% of their monsters, but as I noted before, that isn't much to grant. That would include GURPS WWII, while excluding Empire of the Petal Throne.
The argument then comes that a "large number" of unique D&D monsters are found across editions. I countered that isn't true, unless you are very generous in defining "large number." The argument was put forward that the large number of monsters is only editions of D&D, not settings. That seems nonsensical to me, as we are talking about the "soul" of D&D, not its pantry. Does it matter if Krynn and Dark Sun draw from the same rules set? Do they share a "soul" with Greyhawk even though Krynn has no orcs and Dark Sun has no theistic clerics? Even so, I'll grant it.
And BECMI D&D and AD&D, probably the two most popular versions of D&D of all time, do not share a "large" number of unique D&D monsters. Only at the end of the AD&D cycle, when Mystara become (briefly) an AD&D setting do you finally get many of the unique Mystaran monsters in AD&D... and BECMI D&D never still never had most of the unique and iconic AD&D monsters.
So unless you are ready to claim "Red Box" D&D was not, in fact, D&D, then I think it is very, very difficult to claim that some variation of "all editions of D&D have mostly the same iconic monsters" is true. In fact, I will guess that anyone who is willing to make that claim is probably greatly more familiar with AD&D than BECMI.
Once you exclude real world animals, creatures based on real world mythology, and creatures found in Lord of the Rings, the number of unique monsters shared by all editions of D&D in the 80s is actually quite small.
