It may say that somewhere on blackjackincolor (your statement rings a bell), but you should check to see whether the author (QFIT?) is talking about SD or not. Because SD deals with very few cards, there are weird anomalies with, for example, negative counts getting deeper penetration because n rounds are dealt regardless of how many cards come out and low cards tend to bring out more cards per hand than high cards. So I'm sure there's some rationale for why you might see count asymmetry in a SD or even DD game.
I contend that the effect on a 6D shoe is insignificant.