So, I ran it offline & you are sadly right...
2022-12-29 19:18:48, Info DISM DISM.EXE: Executing command line: dism /Image:C:\ /Cleanup-Image /RestoreHealth /Source:ESD:E:\Sources\install.esd:1 /ScratchDir=C:\BU\temp /logpath:c:\BU\dism.log
2022-12-29 19:19:11, Info CBS Session: 596_442125 initialized by client DISM Package Manager Provider, external staging directory: (null), external registry directory: (null)
2022-12-29 19:19:11, Info CBS Exec: Addsource called, Session: 596_442125, Client: DISM Package Manager Provider, from GPO: No, Path: X:\Sources\ESD:E:\Sources\install.esd:1
2022-12-29 19:19:11, Warning CBS The alternate source path directory could not be accessed [HRESULT = 0x80070003 - ERROR_PATH_NOT_FOUND]
2022-12-29 19:19:11, Info CBS Failed to add new file source [HRESULT = 0x80070003 - ERROR_PATH_NOT_FOUND]
2022-12-29 19:19:11, Info CBS Failed to add alternate file source [HRESULT = 0x80070003 - ERROR_PATH_NOT_FOUND]
2022-12-29 19:19:11, Info CBS Failed adding alternate source directory [HRESULT = 0x80070003 - ERROR_PATH_NOT_FOUND]
2022-12-29 19:19:11, Warning DISM DISM Package Manager: PID=596 TID=1240 CBS AddSource failed with HRESULT=0x80070003! - CDISMPackageManager::Internal_Finalize
It looks like the DISM command is entered correctly going by what I see at TenForums & elsewhere. I don't know why "X:\Sources\ESD" is attached to what it calls the Path in that log. There were other errors in the log preceding this, like three "providers" couldn't load. Also, there was this which appeared twice, but I don't know what file it refers to...
[988] [0x80070002] FIOReadFileIntoBuffer:(1452): The system cannot find the file specified.
[988] [0xc142011c] UnmarshallImageHandleFromDirectory:(641)
[988] [0xc142011c] WIMGetMountedImageHandle:(2906)
I guess I can never recommend an offline DISM again. It's a pity. But thanks for the heads-up.