Folklore, like every village has its own version of the story, slightly different from every other village's version.
There is plenty of documentation on writing a .spec file on the net, but is scattered across 1000 different web sites and mailing list archives. A lot of the documentation is obsolete in places.
You can not go to one place and learn RPM packaging, instead you have to go prospecting like an anthropologist to find all the information that seems to be relevant to your problem.
Every distro does it approximately the same, with enough differences to drive one mad!
Will Linux Standard base or some big documentation writer ever come to save the day and bring order to this chaos?