"I was a bit disheartened to hear that it appears most of the key sound effects and dialogue are contained within the same channel--that being the center channel. Is this unusual? "

While each channel can be a discretely different soundtrack, that doesn't mean it will necessarily be mixed as such. There can be intentional "bleed" from one channel to another to make a more seamless transition from one speaker to another, or for a wider soundstage. As such, whether or not one can isolate music from audio really depends on how a particular soundtrack was mixed.