gentoo is using grub legacy, but the documentation link points to the grub2 documentation on the gnu site. Either the continued use of grub legacy is a bug, or pointing to grub2 documentation is.
Steps to Reproduce:
1. read the grub documentation in the install (grub.conf)
2. follow the link to gnu, to learn more
3. notice that it documents grub2 (grub.cnf)
grub legacy documentation, matching the use of grub legacy in gentoo
I don't know how to describe the severity. It's probably a feature request, since grub legacy is atrophying.
It's neither one of those things.
What happened was that gnu.org rearranged their internal documentation so that the manual/ directory points to grub2, rather than grub legacy. grub2 has serious issues, and will not be the default bootloader for most linux distributions for some time. That includes Gentoo -- it's still hardmasked, in fact.
I'll fix up the links to point to someplace more sensible for grub-0.xx stuff.
Thanks for reporting. Fixed the handbook and the FAQ for the right links.