Sorry, but that is not an explanation for unbalanced consumption of the anion resin and not the cation resin. The total positive charges in water will exactly match the negative charges, and they thus deplete both resins.
The only way one can get depletion of only one or the other resin is if the water is very acidic or very basic (not typical of drinking water) or if there are uncharged ions that become charged one way or the other in one of the resins. CO2 fits that latter description, is very common in well water, and is nearly always the cause of selective anion depletion.
