Confused by the MTR

Today I have been baffled by the MTR; in particular, why is the train going to Sheung Wan from Tin Hau below the train going in the opposite direction, when if you go five stops east to Sai Wan Ho, it's *above* the train going away from Sheung Wan. It doesn't make sense to me, unless the MTR engineers studied under MC Escher (stalwart of the south-west London breakbeat scene, and also the guy who drew those staircases going up to nowhere), and they thought it was a good idea for the tunnels to constantly be moving around one another.