If you turn off animations they ARE loading the menu asynchronously. You'll see a basic menu with the extensions added on as the menu continues to grow and ref

If you turn off animations they ARE loading the menu asynchronously. You'll see a basic menu with the extensions added on as the menu continues to grow and reflow. It's worse if you right click on a file. It also DOES use "loading" placeholder text (e) added the bit about the loading text.