Since the "can rack" is designed for labels to be "not viewable", more than likely it was planned for canned drinks only. Canned drinks are all the same size, and thus are not as likely to jam up. The side-to-side spacing of the "down ramps" of the can rack are consistent dimensionally for canned drinks.
All of those "diet drinks" waiting to go into the fridge have to be somewhere!
So, the can rack is probably as good a place as any for them!!