This reminds me of the old BSL/MLH trick. Basel EuroAirport has two airport codes, 1 French and 1 Swiss; flights out of the French side could be significantly cheaper than flights out of the Swiss side.
Flights were ticketed MLH-BSL (walk, 1 min), BSL-CDG (flight, 45 mins), for example.
Sounds like the same setup. There is no "check-in" as such for the bus, so it's not like they can no-show you on it (or deny boarding on it if it wasn't booked).
Will keep this in mind when booking future AUH tickets, thanks!
