The spec for @vector-unfold ends with the words "the state's value is zero". This is a complete brain fart of mine, and must be changed to "the state's value is <i>seed</i>".
I'm not going to announce a new draft for this, but I have fixed it.
I apologize for not fixing that earlier. Somehow, even though I noticed it, it slipped my mind by the time I had finished the boilerplate involved in publishing a new draft.