The problem with having oil change at authorized dealer(s) is they are independent entity and can have various brand bulk oils, they just use the lowest cost oil(s) that may be used in the vehicles they service, they usually don't use the most efficient oil for any particular car.
They should use 0W20 for the 2015 Altima but they may not have it in bulk, so they use dino 5W30 because it's much cheaper.