Superior Drummer has it's own basic midi engine inside of it. That midi engine controls playback of the grooves inside of the browser and Superior Drummer allows the user certain control over it. Things like soloing specific kit pieces or even previewing the grooves at their original tempos, for example.
Once you pull the groove out of Superior Drummer, it becomes the DAW software's property and it's totally under the host's control from there.
However, if you want to hear a specific instrument, you still should be able to do that by accessing Superior Drummer's internal mixer and soloing that particular instrument from there.