I agree! But it seems that the books all stop at 1850. Or they toss in a few cursory chapters at the end. (If there's some text that doesn't do this, I'd love to read it.)
Answers all the questions, TBH.
Maybe of note, pun intended, Schoenberg was pursuing the "emancipation of the dissonances" while the Bolsheviks were destroying Russia. And of course, that's part of why nobody listens to Schoenberg or performs his stuff -- it's grating and kinda horrible, at least after he abandoned high Romanticism after Opus 5.