It does not isolate grounds, but reclocks and regenerates the signal and uses it's own power supply. Although they state that galvanic isolation is not helpful, I do not believe that to be the case as many people have solved their USB ground loop issues by using a true isolators. Schitt states that galvanic isolation does not help with USB 2.0 data rates, however, even if the ground loop does not affect the digital signal it can introduce analog noise to the Amp or linear curcuits of the DAC, hence noise. Using a true isolator, usually optically coupled, breaks the ground loop.
Good to know. Thanks.