Well that falls in line with Others/Single MC's philosophy; the main LIs want, or at least in his opinion, want someone that can commit to them, or in Sage's case at least, he feels he'd need to commit to her to keep her around. Josy is one such girl who doesn't want to be some guy's notch in their belt, and so he only goes for girls willing to cut loose with no strings attached (so far).
I actually do think that concept is neat because instead of wanting a girlfriend you get to just enjoy college life with your friends. But yeah, Josy put on that outfit for a very real intention regardless of the route, and it's kinda adding to that baggage where deep down Josy still wants him (even if you aren't on the M&J path)