Please log a feature request on Github.
That’s an OSX “standard behavior.” Windows and Linux don’t work that way.
I don’t know how @Vortico implemented the menus, or what difficulties there are in doing native menus on OSX.
IIRC Apple doesn’t make it easy. That’s why people use QT for cross platform development.
It doesn’t change your point about standards, but FYI KDE (and individual applications like Chromium) do work that way.