When set in HKEY_LOCAL_MACHINE\Software\Policies\LibreOffice\org.openoffice.Office.Jobs\Jobs\org.openoffice.Office.Jobs:Job['UpdateCheck']\Arguments\AutoCheckEnabled items for Value and Final, LibreOffice ignore this setting. When set Value to "true" or "false", LibreOffice grayed and check "Check for updates automatically" in in Tools > Options > Online Update. In 93863 was solution to not install update component. But this is not solution for many users.
Mike, could you say something here?
You forgot (or didn't know) about the third element needed there: "Type"="xs:boolean"
Updated https://wiki.documentfoundation.org/Deployment_and_Migration#Windows_Registry with necessary information. Double-checked that it works with the type. Closing NOTABUG.