Microsoft Office does not autoupdate. It notifies you of an update, but you have to confirm the transfer and installation. At least that's how it works on my Mac.
That's because they don't have a robust self-update feature for the Microsoft Updater app. They added an automatic update mode and it appears to be on by default now, which is probably good given the number of exploits Office has had over the years.
On Windows, it updates through Windows Update (which you can moderately control) or through their own App-V/Click-To-Run thing, that updates transparently