I first encountered this in a report of the pioneer nonstop flights New York to Tokyo, by Pan Am 747SPs, where the established reserve contingencies were substantial for flights of this duration. So they dispatched to Anchorage, and then when approaching there refiled onward to Tokyo. I don't know if it was a common practice before that. Certainly back in prop Transatlantic aircraft days they didn't seem too sure on departure how things were going to work out regarding how far they might geton the fuel, dependent on weather encountered, so they were maybe filing for Gander, then refiling for Boston, then finally for New York.