[racket] match-let

In the Racket Reference it gives this example for match-let .

match-let ([(list a b) '(1 2)]
              [(vector x ...) #(1 2 3 4)])
    (list b a x))


'(2 1 (1 2 3 4))

I'm not clear why the result isn't '(2 1 #(1 2 3 4))

If someone could explain that I'd greatly appreciate it.
Thanks,
Harry Spier