Sometimes a reboot can happen when the uninstaller of the app (e.g. Office in this case) wants to reboot the system and it either forces this, or Uninstalr fails to automatically prevent it.
Were there only one app called MS Office 2019 in the app listing, or were there multiple? If multiple, did you select them all? For reference, this is what I see after installing Office 2019: https://ibb.co/NjSym65
To repair this, simply re-install office and then uninstall it.
