But this flight is a one way loop- HKG-RUH-BAH-HKG which means they will definitely pickup passengers in RUH and must get everyone off to clean the plane in RUH.

Though I doubt there will be any religious police to arrest us at the airport but I remember when arriving in Tehran from Europe, there was an announcement on the plane that everyone must wear a head scarf as soon as the plane landed- this included all the air hostess who did not get off the plane in Tehran.

Headscarf is not compulsory in Saudi Arabia but a abaya (long black cloak) is for a woman.