I am missing the part where TFA said that the goal was to help with "basic song writing".

And what is "distracting level of nerdery" to someone can be the key that helps unlock a deeper level of understanding to someone else. I thought we understood neurodivergence a little better these days.

The western theory stuff you describe has almost no relevance at all when considered non-western musical cultures. The contents of TFA, while not strictly comprehensive when considering other musical cultures, is still pretty on point. Even though Carnatic and Hindustani music theoretically uses 22 tones per octave, the most common ones are still drawn from the same set of 12 used in western music, and the most common scales are remarkably similar.