"Which is why such bits of general wisdom exist."
Yes...and they should be stated as bits of general wisdom, IMHO, not as outright facts.
Glamor shots are always supposed to flatter, so will necessarily fall under tighter aesthetic "general rules". Portraits are simply "about" a person, and can be this using almost every photographic technique in existence. I do not like to see "general rules" applied to something as conceptual as portraiture. In fact, it makes my skin crawl a bit. Personally, my favorite portrait pix tend to be shot with normal or slight wide lenses, and they also tend to be shot on location in natural light. This does not mean that other things are not portraits, however, or are not "good".