Dream Drop Distance isn't a sideplot, it is imperative to the continued story that it moves forward.
Holy hell, dude, stop commenting on a series you clearly haven't played (or at very least didn't pay attention to).
Look dude, I define it one way, you define it another. The fact of the matter is, I don't give a shit whether DDD is a spinoff or not. I don't care if any of them are. I just hate the way they did this. I love the series, but damn they could have done this better.