That seems like a distinctly non-romantic "date", so the yuri ships still sail.
Most of the "serial" cosplayers I knew have a huge inflated ego and love nothing more than being admired.
Of the dedicated cosplayers I've known (which is admittedly limited), a lot have been narcissists and attention whores. But not all of them, I know of at least one that was purely into it as a self-confidence boost, which helped her come out.
So the chapter's message isn't inaccurate, in my experience, just not a whole picture. It's an optimistic and uplifting manga, though, so I don't expect it to come out and say "There are assholes in every community."