Most of DCS is still running in those same 2 threads. All the unit AI / flight models / collision detection / line of sight calcs etc are done on one thread. Anything they have done a major rewrite are split off the main thread. The problem is that a lot of stuff remains in this main thread. These threads, however, may jump from one core to another core so you'll see multiple cores being used. Some object loading and stuff may be done in parallel over all the cores though. Don't be fooled, DCS is still mostly the way it has been.