I think it's down to WASAPI being tied to the OS sound system, so in exclusive mode Windows will not play system sounds etc. but with ASIO that's not the case. The ASIO signal itself is bit-perfect but using it does not stop the std. windows sound system in any way so Direct-X/WASAPI etc. are still functioning and sending data to the device in parallel.
10/22/13 at 6:09pm