Yeah, the later Basic etc. sets played down (or even eliminated entirely) the "mock-antagonism" pose, presumably because they were targeted at a younger audience who couldn't necessarily be assumed to pick up on the subtelty, but also perhaps in part because with a few more years' experience observing how people outside their direct circle of influence were playing the game they realized that too many people were misconstruing their intent. Note that Gygax himself kept up (or perhaps returned to) that stance in later years, in his "Up on a Soapbox" articles in Dragon, Actual Play reports from his home games, and in the GMing advice of adventures like Necropolis.The mock antagonism thing was gone by the time I got into gaming. The vibe I got from Gygax, Moldvay, and Cook was an impartial referee who built a reasonably sensible world full of challenges for the players, and then adjudicated their attempts to overcome them as dispassionately as possible. (Not that the DM doesn't care. Only that he doesn't let his rooting for the PCs interfere with running the game.)
So when I got to read some of these earlier Dragons a few years ago, yeah, that reads like antagonism to me. And when I was 10 years old, I'm not certain I would have gotten the subtleties of it. But maybe I'm selling myself short.