The fannie definition is pretty useless which begs the question of how important it is to get it right, or even if its possible to be wrong on borderline cases.
For me, I kind of like at it like this.
Urban = In Town. When you define the neighborhood, its a small area, and pretty much all of it is within walking distance of businesses, it has mass transit, and businesses are scattered throughout the area.
Suburban = Neighborhood is pretty much all residential, some sort of isolation from primarily business districts, some suggest of coherent/planned larger scale subdivision development, has parks, sidewalks, minimal/no mass transit etc.
Rural = The whole idea of a neighborhood is a vaguely absurd concept. Neighborhoods are defined less by location, and more by lot size, property use, drive distance to urban/suburban areas, and commonality of lifestyle/interest preference. There's little or no planning to land division, no tracts, streets are probably not constructed to city standards with lines and sidewalks and stuff like that.
For what you're talking about I'd probably check the rural box, and then describe it as a "small lot tract development in a rural area".