Yup. One way or the other you need to incorporate the round trip distance.
Some equations do this by fudging the resistance values (essentially using the resistance of 2000 feet of conductor, and reporting it as the resistance for 1000 feet 'there and back again')
Others look at the voltage drop on one side only because there is assumed to be no voltage drop in the neutral.
But in all cases there needs to be some consideration of the full circuit.
-Jon
