QAction::setShortcut(QKeySequence::Quit) doesn't map to Control-Q on Linux

It's been visible for a long time in Assistant that control-Q doesn't quit the application. In qttools/src/assistant/assistant/mainwindow.cpp it does this

    tmp = menu->addAction(appExitIcon, tr("&Quit"), this, SLOT(close()));
    tmp->setShortcut(QKeySequence::Quit);