The OSM system is incredibly broad and  vague, with no clear definitions whatsoever. Maine's own definitions are clear, and defined by an authoritative entity, not by the opinions of an insignificant mapper. Have it your way, but you can't convince me that some fool with access to the internet is a better authority than the Maine State Department of Transportation's own classification of its own roads. The DOT creates, maintains, and classifies these roads, not OSM mappers.