The topic has been loosely talked about, for instance at this docs team
meeting:
http://irclogs.ubuntu.com/2015/04/07/%23ubuntu-meeting-2.html
IMNSHO the documentation team currently lacks the manpower needed to
create some kind of end user documentation for phone/touch/unity8. An
initiative from developers and/or other Canonical staff involved in
unity8 is necessary.
@Oliver: The page you linked to is good, but I'm not sure that docs at
that level is suitable to put up at help.ubuntu.com. In any case it's
not the kind of docs which a user who just bought a phone or tablet is
looking for.