on the online installation handbook, where it describes editing /etc/hosts, the actual box claims it's /etc/fstab and an example of an fstab. (someone copying and pasting formatting?) https://wiki.gentoo.org/wiki/Handbook:AMD64/Full/Installation#The_hosts_file
Good catch ; same for x86 : https://wiki.gentoo.org/wiki/Handbook:X86/Full/Installation#The_hosts_file
Indeed, my bad. Fixed.