Overbridge (multi-track) is still in beta testing for DN2 so currently it comes through as one stereo track over USB. When they roll out overbridge (nobody knows exactly when that will be) then it will have multitrack audio over USB, but not until then and nobody wants to use something that’s buggy or doesn’t work correctly which is why they do beta testing, to work out any problems before it gets into the hands of the public.
This is the official DN2 OB beta sign up thread:
I don’t know if they’re still accepting beta testers though.