Wrong, the AMI tool on modern bioses do not perform a “full” dump, only part of bios region, not useful for a regular flash.
Expected behaviour, as you’re trying to flash a modified file and Asus as well the AMI provider are fighting to keep the end user as safe as possible against potential vulneralbilities.
Most likely you will need one… and almost sure that you’d be stuck in that “mod” flash, with a a board to recover and not even a full programmer dump backup made…
The correct accessory to use with the programmer is illustrated here in section " Using AsProgrammer of this guide
Follow the linked guide pointed by Fernando and you may get lucky… this board model doesnt have USB BFB function as one of the options, it may be only option left to use “Flashrom” on AMD platform