I can see why they are naming DAC's R2R, because that's the only way you can get CD's to sound like LP's; that's by recording them and playing back on a good 2 track; in reality, you have transformed digital into analog, because there is nothing digital about the playback from tape.
Technically, they're R-2R DACs, not R2R, and they have that name because of the resistor ladder circuit that they employ. It has nothing to do with reel to reel tape.