...and then the OS blindly follows the application's orders?
Um, that's what it's there for?? An operating system provides facilities to applications, thus making it easier for application writers than programming to the bare metal would be. An operating system that thinks it knows best and randomly refuses to do what it's told is a right pain to all concerned (except of course the BOFH who earns his living by sorting out such messes).
Windows could and should provide a mechanism for the user to override this behaviour
Who is "the user"? The writer of the application? No, you clearly don't think it's her. The owner of the kiosk? The application probably does have some configuration that that user can override. The random punter trying to see whether she can crash the kiosk by pressing buttons in a clever order which she knows ought to do things to the window manager? No thanks.