I believe that you are referring to an article by Henry Tamburin where he states that CSM's actually offer a lower mathematical advantage than a similar game dealt from a shoe.
I believe you get more tens and aces becasue the used cards are not put into a discard tray. Instead they are put back into the cards still to be played.
Michael Shackelford, also known as the 'Wizard of Odds,' did the math on CSM's and you can read about it on his site
www.wizardofodds.com