I mean, a movie release on DVD with just be movie and nothing more is simply not done and many people would consider it cheap and disappointing. The reaction most people who have to a movie that is only 20 minutes long is or a song that was only 30 seconds long is going to be similar: I doubt many movie theaters, radio stations, or content distributors, would consider the "short" sufficient.
In this case, we know the developers have "notes left to play", and could spend the time to do those now. Clearly, I would be the first to point at Apple and say "this is not a legitimate selection criteria" (sufficiently so that even bothering to say it explicitly is kind if redundant ;P), but if I were those developers... this is just a really self-defeating reaction that is not likely to sway either Apple or the people who actually like Apple not wanting to sell things that don't feel "complete enough".
I think we're all in agreement that this sounds like a cool app. I'm just lamenting the lack of creative authority given to its developers, regardless of whatever their future plans may be.