I have the Nordost Baseline made to Rel specs. Yes they are silver PLATED solid core copper (6 24awg wires). Honestly I upgraded my standard Rel cable (aluminum) and the difference was unbelievable. Not puncher bass but a more believable bass. A ton more detail. I even had to cross over at a lower freq and turn down the gain just a hair. So does silver have an advantage over just copper? Can't say from experience but silver is more conductive than copper. That being said typically the electron flow is just on the first few microns of the surface of the conductor with the exception of low frequencies. They tend to ride in the center of the conductor. So your professional expert has a good point in theory. Theory does not always make sense in this hobby. Someday I may try a copper cable but for now I couldn't be happier with what I have.
Sorry I didn't answer you question but I just wanted to share what I know from my own experience.
Sorry I didn't answer you question but I just wanted to share what I know from my own experience.