You are right about most tile looking like dookie if it is not finished. I have been using grout color epoxy on my custom cut bullnose.I can't imagine that unglazed tile edges would be acceptable, but I guess it is?
I am guessing that over 50% of the bullnose made is not hot glazed. Most of the stuff is epoxy coated "Cold Glazed"(multi-tone spatter for alot of the "stone" look tile). I am starting to practice on matching up tile to cold glaze. Once i get ok at it i will make a couple how to vids.