This is no error and does not need a note. OSM will never be perfect and objects will still be missing so this does not need to be noted. Obergartzem is pretty good mapped, there are far worse places in the "Eifel". As I checked Obergartzem had all buildings with an address mapped, the only missing buildings are "extensions"/peripheral buildings like garages etc. Anyway, I added a bunch of buildings. OSM is getting better every day.