If I get hung up on the code, I , like many of us in the field, fall back on what would be the "electrical theory" intended in the NEC.
This becomes harder when influences with other concerns are introduced.
Inasmuch as it can be argued that the NEC is not a document of electrical design,it is also questionable as to it's usage for engineering, safety & liability.
There are hords or resources to address such matters.
I quess , on a good note, and to address the original Q, I would include some more electrical theory intended by codes that seem to go on for page after page.