The myth is the idea that you can fake corporate culture. That allowing and encouraging nerf battles, casual attire, and whatnot represents "corporate culture". Corporate culture is how people are treated, how work gets done, how communication happens, etc. You can pretend to have an open and "fun" corporate culture by faking it with bouncy castle parties every month, but at the end of the day if you still have a culture of scapegoating, blame, and problem avoidance then that's your true culture, not the fun and open facade.