the version on the twofer coupled with Old Folks At Home is a totally realized medley and arrangement. aside from Brian's vocal flub on the first verse, it is a finished track.
Weren't there more vocals to be laid down on the second half of the track? Sounds unfinished to me.
I'm not sure what exactly Brian was planning on doing with this tune, but yeah I'm pretty sure he left it in an incomplete state. Fortunately for us, incomplete Brian Wilson works like "Do You Like Worms", "Child Is Father Of The Man", and "Old Folks At Home/Ol' Man River" are usually even more enjoyable than finished works by a lot of other artists. Shows just how good his stuff is.