Every BIOS update I have done on my ASUS X670e Plus board, I save before hand to USB update then restore.
There was only the once when there was a big jump in revisions where that the saved file wasnt accepted.
No tricking involved it just either accepted the restore file and worked fine, or simply refused to load the file.
There probably is some kind of check that happens and if it realises that the older save file will cause issues refuses to load it.