Neighborhood That Never Was

Today I present a real mystery. Pictured below is a portion of Hagstrom's 1945 map of Somerset County showing portions of Hillsborough and Manville. Route 206 - then designated as Route 31 - is at the left, and Manville's Main Street is at the right.

Just east of Route 206, south of Duke's Parkway, there appears a grid of streets with avenues named Hamilton, Sylvan, Roselynd, Frazee, and Garretson, along with Lewis Place, Ellis Place, Vance Place, and Jean Place. The east-west streets are extensions of Manville's Green Street and St. John Street.
 

An examination of aerial photographs taken both before and after this map was produced - in 1931 and 1956 - show nothing but cleared farmland on this tract. This parcel appears to have remained farmland until the Campbell Road/Nostrand Road development was built in the 90s.
 

Was this an early plan for a post-war Hillsborough housing development? If so, it would have predated Green Hills, its eventual neighbor to the west, by a decade, and New Jersey's famous cluster development, Village Green, by 15 years.

Ideas anyone?