Starting with Windows 11 25H2 Build 26200.7019 (or 26100.7019 on 24H2) and newer, “Update and shut down" will shut down, not ...
So, when you click "Update and shut down" on your PC, you assume your PC will install any available updates, then shut down.
Microsoft has confirmed that it's testing a fix in the latest Windows 11 preview builds that is supposed to address a long standing bug with Windows Update, where the "update and shut down" option ...