"Sabayon is considered 'close' to Gentoo, but not necessarily
'very close' (at least in my view). The reason for this is because
Sabayon uses its own versions of some pretty major packages
(browsing through their overlay, I see packages like grub, xorg-x11
and xorg-server to name just a few).
"The problem is not that we (the Gentoo community) don't want to
provide official support, it's that we can't (beyond a certain
point). Sabayon provides its own version of many packages and these
seem to (sometimes) lag behind the official Gentoo tree..."