Hmm.  Let me rephrase that.  *Internally* it doesn't support bytes payloads, it "encodes" bytes payloads as surrogateescaped ascii, as you have oserved.  Which is why this is on the borderline, and could possibly be considered a bug fix, because from an external point of view it does support parsing and generating 8bit payloads.

I need to give it some thought, and perhaps others will weigh in with opinions.