Correct. If you have two rims of different aero-ness, putting the most aero on the front will yield the least overall drag. Of course crosswinds affect the front wheel more so most run as wide as reasonable for the conditions in the front and wider in the back, and this is what looks normal to most. Weight may be a factor too, and deeper rims weigh more than shallower in the same model line. Going narrower in the rear can save some weight while not having as large an impact on drag.