"mouse gives focus to hovered window" issue when another window is fullscreened (F11)

When some window has been fullscreened (F11, no menubar nor titlebar)
then the "focus is given to window under mouse pointer" is broken :
it brings the fullscreened window on top, even if it should stay behind some other new window.

Steps to reproduce
- open unity tweak, go to "Windows management" tab > "More" (last subpane)
(my UI is french so i'm unsure with english labels)
- choose "Focus" > "Autoraise" + choose "Sloppy"
- open Firefox (for example)
- press F11 to make it full screen
- open any other app (geany or libreoffice for example)
- bring mouse on center of this new window
- See : Firefox is brought to front and other app window disappear in the back.

On Ubuntu 14.04