Yes, this should certainly be mentioned. Will work on it more tomorrow. My concern was that the lower tip of the triangle varies quite a bit with what many sources still call Rembrandt lighting. Some have the tip only going down to the nose (or not even that far), whereas the key triangle I showed (and the Rembrandt style which is just a more side-lit "loop lighting" that you mention) extends down to about the side of the mouth. I guess this also depends on how full the person's cheeks are though, and the classical Rembrandt style paintings tended to use people who were more voluptuous
. The rationale is that having the tip extend all the way down to the mouth errs on the side of avoiding any chance of darkening under the eyes or within the eye socket.