fedora will also patch stuff from upstream to include in their distro. for better or worse arch will try to upstream the patch and if they don't like it just keep an older version around if they don't accept it
https://src.fedoraproject.org/rpms/grub2/tree/rawhide
Some of these are pretty questionable, particularly disabling the use of "grub-install" on UEFI systems (https://bugzilla.redhat.com/show_bug.cgi?id=1917213)