Yeah, I think the intended conclusion is just that the JoJo crew are a bunch of quirky weirdos who like talking about weird things in their free time.
I mean, this is a gang consisting of a 20-something who acts like a kid and can't do basic arithmetic, a guy who's pathologically afraid of the number 4 and an ex-cop who thinks pissing in someone's tea is a hilarious prank (Bucciarati and Giorno are the most "normal" members of the team, at least at face value, and they mostly stayed out of that conversation). Misunderstanding vegetarianism would hardly be the oddest thing they've ever done.