Comment 7 for bug 1681290

Forgot to mention, menus in gnome-shell itself (top bar, dock, and other panels) do not suffer from this delay. They close immediately. This ticket is associated with gnome-shell, but the way the original author describes it, the shell isn't affected for them either: "This occurs in GNOME, GNOME applications and also for non-GNOME applications such as Firefox and Chrome."