It is true that zoning laws in many cities only allow detacted single family houses or tall condo buildings to be built and nothing else, any residential property that is not a detacted single family house or a condo building is referred to as "missing middle" housing. These include smaller apartment buildings, multiplex housing, mixed use properties, etc. Some American cities are getting rid of the single family house zoning regulations and making way for different residential properties, Europe doesn't have single family zoning like America does and allows all kinds of properties to be built, here is a video on it: https://youtu.be/CCOdQsZa15o