Glad you have a workaround. I think the cause is the Windows boot manager certificate change, not the image.
Your golden Optiplex installed Windows with Secure Boot on. Windows servicing then added the “Windows UEFI CA 2023” certificate to that machine’s db, and switched the boot files to a boot manager signed with it. The other Optiplex 3000s only trust the 2011 Microsoft certificates, so they reject that boot manager. bcdboot works because it copies the older 2011-signed boot manager.
Can you confirm with two checks, in admin PowerShell, on the golden machine and on one target?
[Text.Encoding]::ASCII.GetString((Get-SecureBootUEFI db).bytes) -match 'Windows UEFI CA 2023' mountvol S: /s (Get-AuthenticodeSignature S:\EFI\Microsoft\Boot\bootmgfw.efi).SignerCertificate.IssuerIf the golden machine says True and the target says False, that is the cause. A newer Dell BIOS may include the 2023 certificate in its default keys. I am also looking at having FOS add it during the Secure Boot enrollment task.