The search works well most of the time, but occasionally some addresses will return the city instead of an address. Is this normal?

Sorry for the confusion. You can read about the behavior in the Quality section of the Geocoding Response docs.

The geocoder will always try to return a response, even if it wasn't able to find the address. This may be helpful when an addresss doesn't exist or is brand new, and some level of location is better than none. If you do not want to use this information, depending on how specific you need the results, you can consider everything with a quality of 6 and lower as no result.