I'm not sure the existence of towns in North America called "El Dorado" really puts paid to the question. It's an imaginary town in song and legend (as one says), and going and naming a real town after it doesn't change that, nor make the songs and legends suddenly "about" the real town. They're still about the imaginary town. (Barring somebody writing a tongue-in-cheek song about one of the imitations.)

O..O
=o=