The Andaz Singapore is taking a page from airline Basic Economy fares, offering a new ‘room only’ rate. When you think of room only, you may assume that it simply excludes breakfast or other inclusions. In this case they mean it literally: you can stay in the room, but have no access to the hotel’s gym or pool.
This also lets them sell rooms for less on third party websites without running afoul of best rate guarantees, since the restriction doesn’t apply to Hyatt direct booking rates.