In the all the textbooks I have or have seen, those are called "acoustics" (and more specifically "tuning and temperament"). They are covered in the text book I had for acoustics, and not covered in any of the textbooks I used for theory (jazz or classical). For example, in Rossings "The Science of Sound", it's in a chapter called "Musical Scales and Temperament".

Look, I agree that they should be. I have literally had discussions with one of my PhD supervisors (who taught acoustics) about how much better some students would understand some of harmony if they started with some acoustics! But they aren't, so if one is going to redefine common uses of terms, at very least this should be explained in detail to the student prior to use.

My call on this stuff is always determined by "What will help my student learn most efficiently, without frustration or confusion". That article fails badly on that count.