This is a stupid question.
They call it DLC (downloadable content) because it's not all just a single map. There's places you can go into, right? Those are completely differential in terms of generation of the bytes of data within the "map." If DLC was classified into a literal and single map, everyone would be wasting their money because it would be a useless investment.
And for the Legion, there are ghoulified persons in Lonesome Road that used to be affiliated with the faction.