Comment 12 for bug 1954456

So I think that in the -minimal case, since we do not have a kernel, when we install the package it runs kernel-install and creates a BLS entry for the running machine-id. Thus grub2-mkconfig works.

I believe that grub2-mkconfig not updating all installed kernels is a regression. Previously it seems it would update the kernel options in the global grubenv file, which was included by all BLS entries. After an upstream change, this no longer happens.

I have explained and suggested a fix in https://bugzilla.redhat.com/show_bug.cgi?id=2032680

I would suggest to keep the bootloader as simple as possible and work around this behaviour for the centos element. https://review.opendev.org/c/openstack/diskimage-builder/+/821772 is a proposal for something like this.