Menubar clicks are inconsistent when an app is maximised

(13.10, unity 7.1.2) When an app is maximised in the background, it will receive clicks on the menubar/titlebar even if another app has focus. This can cause a very jarring user experience if they are a couple of pixels out when clicking a menu in the focussed app, as the app they're using owns part of the titlebar, and the maximised has the rest. There is nothing on screen that indicates this. See http://www.youtube.com/watch?v=yZHiDeqH78E for a demonstration.