Just doing some more research on this, found this blurb in the new terms for Win 11:
This option is new starting with Windows 11. Specifying /EULA accept instructs Windows Setup that the end user license agreement has been accepted. Starting with Windows 11, acceptance of the Windows EULA is required before Windows Setup installation begins. By specifying /EULA accept you are agreeing that when applying this operating system either (1) the applicable Windows license was purchased though volume licensing, or (2) that you are accepting the relevant Microsoft Software License Terms. Windows Setup will return error MOSETUP_E_EULA_ACCEPT_REQUIRED (0xC190010E) if /EULA accept is not specified and (1) /Quiet is specified, or (2) if Windows Setup is started where user interaction is not supported. To learn more about licensing, see Microsoft License Terms.
The last part seems to say that it will always fail if you either specify /quiet or start the upgrade from somewhere user interaction is not supported, so I guess that includes a PS script?
If I am reading this right they have made it completely impossible to script?