The Verizon mix for 32gb was about ten to fifteen percent depending on channels. Given the storage issue of the 16, even a conservative extrapolation going forward suggests impact if not considered.
I agree with your premise. The point is complacency in light of their apparent ignorance does not seem to be a sound tactic. If they really think an sd card fixes everything, why stock anything else?
Added: You would hope both demand and the extra margin for the larger size models would be enough of an influence.