INTERESTING, these are all such juicy points. In a context of such accept homosociality, maybe he doesn't actually read as that slow on the uptake as he at first appears. And it's true that he does seem weirded out, not by the Earl's familiarity per se, but by the fact that he's so familiar without knowing Rory that well, so it's unearned. (Which is consonant with other 18th & early 19th century novels I've read: unearned familiarity is always a red flag). In any case, what a find!