Hi, just saw ur query on wiki. As you can see with most of the map, the house number is added to the building as part of the building address instead of entrances as there are likely multiple entry points to a building.
You can crosscheck the house number with the Singapore OneMap overlay (which also puts the house number in buildings) but the one used for osm iD might not have been updated with the latest version on the official gov website so newer buildings might not show up
Hope this helps