I can understand your skepticism towards the concept of the maturing hairline, abcdefg. I don't think the science has been worked out precisely enough to convince everyone that this apparently happens regularly in non-balding males. I also don't believe that the photos Rassman used to illustrate his points were effective. A better example of a "mature hairline" would be Pierce Brosnan's. Compare photos of him when he was young to those of him today, and you may see the very gradual recession that occurred over the years before locking into a NW2 pattern.
This process does not occur in all men -- David Bowie, for example, has retained a Norwood 1 hairline his whole life. To add further confusion, a lot of famous non-balding men may conceal their "mature hairlines" through styling or hairline lowering procedures, so we rarely get the opportunity to inspect their natural hairlines as we could Mygoodness' in this thread. In this way, the media can distort reality and make people like Mygoodness freak out over the slightest recession, even though it can be normal for some.
Rassman says that where the recession stops in non-balding males depends on genetics, so there's no hard rule for where the "mature hairline" must exist. With the marker, I assume he was just guessing based on trends he's observed over the years (around .5" above top wrinkle in the center and 1" above top wrinkle at the corners). There can always be deviation from those figures. Some men stop at Norwood 3 -- this is where I disagree with Rassman, since he doesn't think that could be considered a "mature hairline." You see, the theory doesn't always make sense.
Also -- I want to clarify that I'm not an expert on this and can't claim I am, so please take what I've said with a grain of salt. It may be wrong, but I usually trust the doctors who have had much more experience studying this than I have.