QMenu / cocoa... False warning (?)

Under Cocoa, 5.0.2 issues a warning and prevents inserting a QAction if this one is already used in the main mac menu.
The warning is "Menu item is already in a menu, remove it from the other menu first before inserting"
and can be found in QCocoaMenu::insertNative

However, there was no such warning in 4.8.3/Cocoa and everything was fine. And in 5.0.2 if I bypass this warning and the "return" code, then no problem, everything works fine as in 4.8.3. Therefore I am wondering if this warning (more than that, actually, as there is a "return"), if really justified.

I use this possibility a lot, to show context menus from main menu's parts.