I've just tried this out, and found that the melody is 4 bars ahead of the accompaniment. I don't think it's just my setup, because the lyrics are out of step too - the "dance" of "Missed the Saturday dance..." should line up with the descending sequence C6 D Eb Em7, and the "out" of "without you" should line up with the four bars of walking bass.

Odd, because the arrangement of the backing is a brilliant demonstration of the power of BIAB!