Someone treats "the vagus nerve" as one thing, or a diagnosis of stress or depression doesn't match the body's actual state.

The single load-bearing anatomical correction the whole book stands on. The old stress/relaxation seesaw treated the vagus as one "rest and digest" nerve, which left depression and shutdown with no physiological model at all — you cannot explain freeze with a nerve that is supposed to calm you. Split it into the ventral branch (myelinated, mammalian, social engagement) and the dorsal branch (unmyelinated, ancient, shutdown), and the symptom map reorganizes around which circuit is stuck on. "There is actually no direct anatomical or functional connection between the two; they are separate and distinct entities."