No idea, (and I'd be interested to know why too) but it's not that uncommon. The other evening I watched FDX001, a 777 start off from its stand at STN, taxi to the threshold of runway 23, power up and take off. Interesting to switch to satellite view : it's pretty much bang on for position of taxiways and runway.
Planes disappear when they land at NRT and HND, but I can watch them taxi to take off from HND. It's impressive how quickly they clear that new runway and make that bank over Tokyo Bay. It's also fun tracking the 787 flights.