NAA Clock Timing Improvements w/Asynchronous USB?

Can a Networked Audio Adapter (think Sonore or SOtM) improve the timing of a DAC using Asynchronous USB? These manufacturers place a lot of emphasis on their clocks...the SOtM even has an external connector to upgrade to an expensive master.  I thought the big revelation of Async USB on a DAC is that it no longer extracts clocking from the USB packet and frame timing signals and thus will use its own clock?  However, it's hard to believe that the timing improvements that these vendors brag about apply only to adaptive or synchronous USB.  These devices aren't cheap and I hear many folks raving about them.  Thx