There is one way I can make the fever dream work. It just relies on what is not a very flattering reading of Wash in the beginning, though it leads to character growth later on. Wash telling himself "I was just following orders" about Donut kind of unambiguously demonstrates that he still hasn't taken responsibility for what he did in season 8. But Locus's fixation actually pushes Wash to self-examination and from season 12 to season 13 there's a change in him--by 13 he is actively saying, "No, FUCK YOU, I am NOTHING like you, and what I did do, I take responsibility for and I've changed."