Thanks for the reply.

The primary reason not to repeat the same information is that OSM is a geographical database. Doing so guarantees better data consistency.  This is particularly true in a place like Brussels with multilingual street names.

I understand that some people would prefer that every POI contained all the information, to obtain everything with a single query.

Most reverse geocoders automatically understand address inheritance, for instance Nominatim, which will automatically obtain the address of the container building (https://www.openstreetmap.org/way/228248709) but also post code areas, nearest city node, country, etc.

Have a nice day.