Ninja T4 might be the template technology behind all this stuff, but it's hardly going to be what your end users are thinking. They're looking at the demo site and maybe even the template they've downloaded. I can assure you that "T4 template" documentation was the absolute last thing in my mind when I was trying to figure out how to get rid of this thing.
People at JoomlArt are going to be into the template technology way deeper than your users are. I know there is a lot of work in good documentation (and can appreciate the work done to date) but we need this sort of thing included.