Microsoft has probably modified the way in which Automatic updates are delivered and installed on your Windows computer.
With Automatic Updates enabled, your computer would download the necessary hotfixes and patches from Microsoft Update website, install them in the background and then constantly irritate you with an annoying "Restart Now / Restart Later" message box.
That functionality hasn't changed but you will see a slightly modified version of the "Turn off Computer" dialog when you have updates in the installation queue. (see screenshot)
Now there's an option to install the important updates before shutting down the computer. Or if you are in a hurry, you may turn off the computer without installing the updates. Neat.
Related: WGA Update is now mandatory.