When menu role is set to AboutRole or PreferenceRole, And modal dialog is shown, about menu  from App's menu is still clickable. 

(These menu role is set to place it under right menu item otherwise it goes under "help" menu if text is not in English)

Attached example shows it. Run the example and click last button to show a modal dialog and then try to click about dialog using Apps menu

Note, Same example is also used to display other QprogressDialog issue in QTBUG-80272