What you probably have is a component of O365 as an updater installed - check your programs and features because msft bundled this awhile back and once its removed it will stop the update treadmill.

Didn't they create Windows Installer (i.e. MSI) originally to meet the needs of Microsoft Office? And now they have MSIX to replace it, both of them built into Windows, but they still need a third installer system for Office, which is now also apparently built into Windows?