This will have an endless oobe/setupcomplete phase, when using dism commands to add updates, etcetc.. Maybe have a look here too: https://forums.mydigitallife.net/th...etupcomplete-firstlogon-silent-install.73131/
I tested it, with no problem, RunOnceEx is executed after OOBE is finished and also after SetupComplete.cmd is finished. When OOBE.cmd is launched its only adds the registry entries for installing on first login