A book that aims to examine 20th Century American Literature is likely to focus on "literary" authors like Hemingway, Faulkner, Roth, and Morrison. And -- unless the aim is to examine "popular fiction" -- it's unlikely that the book will focus on Michael Crichton and John Grisham, even though these authors probably sold more books.
So, I can see how there would be a similar distinction in the jazz world -- between music that's more commercial as opposed to music that's more artistic. Of course, this is all a relative thing and subject to change over time. (For many years, many people in the musical critical establishment didn't consider ANY jazz to be artistic!) So the definition of "artistic" is always a moving target. Furthermore, sometimes the commercial and the artistic are an overlapping Venn diagram. (See Ellington, Edward K.)
Ultimately, I think what should be included in our theoretical book really depends on the author's intentions. What is the scope of their examination? Is it all jazz -- including the "pop" forms? Or is it limited to the stuff that's (relatively) more "artistic"?
My 2 cents.