Full Screen mode on Mac OS X doesn't supress Menu bar if custom Menu is created

If a window is switched to Full Screen mode on Mac, then it doesn't result in Strict Full screen mode with Menu bar being visible when mouse is moved to top of Screen

This problem only appears if a Custom menu is created using system-wide menu bar(QMenuBar(0))
If default menu is used, then Full Screen mode window results in Strict full screen mode and Menu bar is not visible.

Look at attached sample code, if code to create custom menu is commented out then this problem doesn't occur and no menu bar is visible