dding grub2 onto PReP partition renders grub2-set-password ineffective

Description of problem: If one uses dd to copy grub core.elf onto PowerPC PReP partition (needed for Secure Boot to work) then grub2-set-password no longer has any effect

Version-Release number of selected component (if applicable):
grub2-2.06-53.el9

How reproducible:
always

Steps to Reproduce:
(optional) 0. grubby -title 'Test entry' --add-kernel /boot/vmlinuz`uname r` --initrd /boot/initramfs`uname -r`.img --copy-default --make-default
1. grub2-set-password
2. dd if=/usr/lib/grub/powerpc-ieee1275/core.elf of=/dev/sda1
3. reboot machine and attempt to edit the boot entry

Actual results:
It's possible to edit the boot entry without being prompted for user name and password

Expected results:
grub prompts for username and requires correct password in order to edit the boot entry

Additional info:
Regardless of the order of dd and grub2-set-password, it does not work: reversing command order and / or running grub2-set-password again does not fix it.
Same results with Secure boot enabled and disabled.
/boot/grub2/user.cfg gets created and remains