> Now, the article did mention "infill" which sounds more urban, so maybe there's a difference in the city and county of Seattle?
Seattle is in King County, which has a total area of 2,307 sq. mi. This is clearly referring to the city proper, which is, as you note, still much bigger than the City and County of SF, and much less densely populated to start with.
Seattle is in King County, which has a total area of 2,307 sq. mi. This is clearly referring to the city proper, which is, as you note, still much bigger than the City and County of SF, and much less densely populated to start with.