Good point about loss of information from historical, technological and cultural restriction. My reasonning is based on what people today call music theory in most schools and below a certain level. Surely Berklee talks about all kind of stuff.

I don't think all was lost, things that weren't writeable could be passed orally as virtuoso techniques that weren't deemed useful to be written for the average player anyway. See how Spanish guitar technique has survived time.

My attempt at understanding jazz is that it revolves rhytmically around swing. And that core swing can be described through a tinier and principled abstraction rather than a crude ternary feel mark left for the student to figure out. Also from trying to make sense of jazz music without the traditional formalisms (I barely know two modes, and never learned that many progressions). There are some tiny tiny notes in Herbie Hancock playing that shifts the whole world. I'm sure "the" truth lies in there. see the finale solo https://www.youpak.com/watch?v=95TAfOWJKwg