I think that's the case at non-Aisle locations (called Emerald Counter service and at these locations). Emerald Aisle locations (here) shouldn't normally do that, though they might if you reserve a specific car class and it's not an Emerald Reserve location--at Emerald Reserve locations, non-Aisle reservations get sent to a row corresponding to that class, whereas at non-Reserve locations, non-Aisle reservations will get assigned a specific car. At least I think that's how it works; been awhile since I've done a non-Aisle rental.