Then we have configuration split over two completely different
formats.
It's kind of unappealing.
As a person who maintains software that has to interact with many
bootloaders, I love the BLS. It's a far saner proposition than having
to interact with many of them, particularly grub2.
That said, there is also momentum for bootloaders to be able to read
the syslinux format.
https://fedoraproject.org/wiki/Changes/u-boot_syslinux