On OS X it's somewhat rare for an update for require a reboot. Often they don't actually reboot the machine but just log you out, perform the update, and then log you back in.
While these updates feel like a reboot since you lose your desktop environment state, you can tell the difference if you're paying close enough attention.
Oh so they still have those in Win8. I didn't miss that when I moved to Linux. Reboots for Updates is a broken concept.