Great article. I think there are a couple points that need emphasizing: 1) codes and standards only have legal authority to the extent that they are adopted by a governmental body (city, county, state, etc.); and 2) the governmental body may adopt all or any portion of a code and modify it in any way that they see fit.
In addition, most governmental bodies reserve the right to modify what's required on any specific project despite the adopted code. So the bottom line is, the code is what the AHJ says it is, regardless of what any written document might say.
So, your point about getting the AHJ's input early in the design of the project is essential. However, this is not always as easy as it sounds. I have experienced building officials who were reluctant to make commitments in writing, had different officials within the same agency offer different interpretations of the same code, and had officials change their mind after a project was completed. (If you look at plan approval stamps, they almost always say "subject to field inspection" or words to that effect.)