Originally Posted by Brian278
IMO the button down collar tends to be rather associated with trad, a group not particularly well know for their, shall we say, progressive stylings. The overall theme of slim-cut one button suit, skinny peak lapels, skinny tie, eye catching socks, low-ish profile shoes, etc., is generally "fashion forward", at the risk of conjuring up the negative connotations of the term. So perhaps it's my own penchant for the cleaner look of a non-button down, but I think the general aesthetic is better complemented with a sleeker smallish semi-spread or standard point.
Either way, GS pulls off the contrasting elements effortlessly as usual.
Button down collars have been a Mod staple since the beginning, since they got into the Ben Shermans with long collar points and buttons. Without a jacket they almost (ironically) look sharper because the collar points can't go anywhere. And much of the Mod look comes from the American Ivy stuff you're thinking of as well.
Personally, with a jacket, I prefer a not-button-down collar, but in terms of the aesthetic and the "rules" he's working within, it's totally correct.