Valiant said:
Dragon is not part of the core rules. The DMG says the player sticks to the PH.
No it isn't. But then again, in those days no one was as rabid about what was "core" and what wasn't. In point of fact, someone making an argument about "core" would likely have been laughed at, loudly - house ruling was not only accepted, it was expected.
However, that's beside the point. You said before the internet we poor benighted fools playing 1e had no way of knowing how Gygax and his crew played D&D. You were wrong. We had
Dragon, we had conventions. We got information from those sources concerning their games, how they played, and so on. Which has nothing to do with whether
Dragon is core or not.
And you still haven't even bothered to address the fact that in most groups, it appears that DMing duties rotated. So even if "players" stick to the PHB, there will be several people at the table who have studied the inside of the DMG, "legitimately" under the "core rules" because of their prior stint(s) as DM. If the rules are designed to give a good play experience only if you are ignorant of the rules in the DMG, then they shouldn't have been having any fun as players.
But the opposite appears to have been true - almost univerally, people who had DMed and/or had simply seen the inside of the "magical, wondrous, forbidden" DMG enjoyed the game
more, not less. Which runs counter to your assertion that the game is more fun when you are playing Calvinball. And since this is the way we know that Gygax and his compatriots played, we know that the game
wasn't developed with the idea that players should stay out of the DMG at all costs in order to enjoy the game. because it seems like most of Gygax and his buddies somehow had lots of fun playing the game even though they all knew the material that would end up being the contents of that book.