Floating Indexes

In Blackbelt in Blackjack Arnold Snyder relates that one reason why highly rounded indexes don't affect your results is that the actual index number moves around due to various factors, one of which is the current level of penetration.

I've been wondering if some unbalanced counts may unintentionaly be partly accounting for this in the apparent inaccuracy of their indexes early and late into a shoe, improving their results.

Has anbody investigated whether there is a consistent penetration effect on index numbers? Maybe there is a complication in there worth learning, something like "for a 6 deck shoe add/subtract from the index x * (number of decks played)."