I think we can leave the situation as it is, with the ways you mapped as access=no.  (highway=track + ski=no is probably a little better.)

I could not find any online documentation about the situation here.  It can only be done through surveys to have a complete view of the no-skiing area.  But there is no known active mapper in this part of the country and already too many open notes.

Sometimes, we must accept that we cannot fill everything on our map.