This undoubtedly comes across as a publicity grab. The delivery drones aren't carrying large packages, and it's relatively easy to handle a modestly-sized city with few big buildings. However, it does show how delivery drones might find early use in cities. Rather than try to serve everyone, merchants can use drones in those situations where terrain or buildings make ground-based deliveries particularly difficult. Essentially, they would iron out the kinks in the existing delivery system -- instead of waiting ages because you live in the "wrong" part of town, you could get deliveries as quickly as anyone else.