Floor Plan Errors

Super excited when we first got the floorplan from HDB. However, then we realised floorplans can be quite wrong... (we checked with neighbours regarding the layout, door of our entire block)

1 contractor says long long time ago, such old flats always have such "missing" features where $$ disappears into other people's pockets.... ours is 26 years old.... the original floorplan should be hand drawn and not such digital sketch. Guess the person who did it the newer digital drawing never check.