I think it was posted in the thread about the accident involving JL516; due to runway 34R at Haneda being out of action (believed until Monday 8th Jan), the remaining runways available for takeoff being shorter and so the aircraft can't take off with as much fuel.

Others have mentioned that NH are not taking this approach but you can understand why JL are being extremely cautious at the moment, a couple of hours' delay is fairly minimal considering what's gone on this week.