I don't expect the value to change if the firmware configuration doesn't, but if CSM is enabled, then it *might* not report amd64/efi; and the fact that you disabled CSM since then changes the behavior of the firmware. *However*, this gives me something to look into some more; it's possible CSM on that firmware (I think I tested this combination on Lenovo firmware, but not others) doesn't expose all the EFI variables needed.
I don't expect the value to change if the firmware configuration doesn't, but if CSM is enabled, then it *might* not report amd64/efi; and the fact that you disabled CSM since then changes the behavior of the firmware. *However*, this gives me something to look into some more; it's possible CSM on that firmware (I think I tested this combination on Lenovo firmware, but not others) doesn't expose all the EFI variables needed.