Fun fact: every side of an interchange station (except NSEWL-only interchanges: City Hall, Raffles Place, Jurong East, Tanah Merah) is designed to operate independently. You can see this in your SimplyGo app. It means extra bureaucracy with more staff than really necessary, no data linkages which means a staff on one line can't see the CCTV in other lines' areas (and also why there's no train timings for other lines at some interchanges), and many other inefficiencies and related costs.