Code to reproduce :

    @Override
    public void start(Stage primaryStage) {
        BorderPane pane = new BorderPane();
        Menu fileMenu = new Menu("File");
        Menu aboutMenu = new Menu("About");
        MenuBar menuBar = new MenuBar();
        menuBar.getMenus().addAll(fileMenu, aboutMenu);
        pane.setTop(menuBar);
        pane.setCenter(new Label("Center label"));
        Scene scene = new Scene(pane);
        primaryStage.setScene(scene);
        primaryStage.show();
        primaryStage.setTitle(VersionInfo.getRuntimeVersion());
    }

Steps to reproduce :
1 Move mouse cursor to about menu
2 Press F10 - you will see two focuses - File and About