To put it plain, this is simply not correct. DCS does *NOT* use all available cores. In every particular time it is using just one core. All OS can do is move it rapidly from one core to the other in order to do some cpu thermal/stress/load ballancing. Then what you see in task-manager is very little load on all cores, but it is averaged over certain time.
It is not always like that with "any other application". There are apps that can use effectively all cpus/cores you have.
Edit: IIRC, DCS is two-thread app, sound is handled by separate thread. So it can use "one and a tiny little bit of the second one" cores (sound does not need much cpu-power)...
