Comment # 1 on bug 939453 from Chris Murphy

https://bugzilla.opensuse.org/show_bug.cgi?id=848609#c3
I'm confused by this. Why is gptmbr.bin being used, unless extlinux is the
bootloader? If GRUB is the bootloader, grub2-install should write boot.img to
LBA 0, not gptmbr. And boot.img contains the jump code to find core.img in
BIOSBoot, so there is no need for legacy_boot attribute.