Frankly, that just sounds like a fire code / building code issue. Are these "apartment buildings" legal for habitation, with actual legal separate apartments, and not some weird subdivision/subletting situation?
In every place I have ever lived, having a clearly marked addresses and door numbers for apartments is required by the fire code. If there's an emergency that requires a fire or ambulance response, smoke in the air, etc, then "Nth floor, door on the right" is not a good thing to be explaining over the phone.
> Are these "apartment buildings" legal for habitation, with actual legal separate apartments, and not some weird subdivision/subletting situation?
Yes. In fact the 'résidence' (the conglomeration of apartment buildings) is considered one of the nicer, more desirable, places to live in the city. In the US, each apartment would be called a condominium [1], i.e., most are individually owned and not rented out.
In several countries in Western Europe there's hardly a tradition of apartment numbers in multi-apartment buildings. Instead the apartments are identified by family name of the owner. Or the main person living there. Or the person who used to live there some time ago. Or some guy backpacking in Asia and (illegally) subletting the apartment.
In every place I have ever lived, having a clearly marked addresses and door numbers for apartments is required by the fire code. If there's an emergency that requires a fire or ambulance response, smoke in the air, etc, then "Nth floor, door on the right" is not a good thing to be explaining over the phone.