Your blog is wonderful, an excellent information source. You are also one of the few who mentions the mature hairline in a significant amount of detail. So many people get mislead by the classical Norwood 1 image, which is actually a juvenile hairline, as you said. (Many sources claim that only NW 1 means a full head of hair, and everything else is a sign of balding..)
That said, there is something you haven’t mentioned, but seems to be relevant: the size and shape of the head, especially the forehead.
NW 2 hair tends to look more dramatic on people with round faces and large foreheads than on oval heads, for example. In addition, I have noticed that some foreheads tend to have a more rounded shape, while others look more like a V (when viewed from above).
Do you agree on this?
The Norwood hair loss classification describes the variations in male hair loss patterns. It is not the progression or stages one goes through. You can look like you have a full head of hair, but still be a Norwood 6 if you show the thinning pattern. Some may be a Norwood 3 and be that way for the rest of their life. In other words, Norwood 3 rarely, if ever, progresses to a Norwood 6.
With respect to the shape of one’s forehead or even the shape of their head, I agree it may exaggerate the look of a Norwood pattern, but forehead shape and hair loss are not directly related. Perhaps there should be a forehead classification.