You seem to pre-suppose that all-rights-reserverd copyright on a manual for a free software program is OK. I do not agree, mainly for the reasons outlined here:
No, I don't. I merely think that having a free manual and a non-free alternative to it is perfectly fine, because the user will decide which one they pick. No need to force any kind of specific ideology upon anyone.
https://www.gnu.org/philosophy/free-doc.html