https://docs.freebsd.org/en/books/handbook/boot/#boot-introduction mentions GRUB. Some readers will wonder why things such as installers for FreeBSD are not suitably GRUB-aware; and why there's so little FreeBSD-provided documentation about GRUB.
Add a note, directing users of GRUB to GNU-provided documentation.
Case correction: GRUB should be uppercase.
Elsewhere in the page: a minor correction, superfluous space before a colon.