The SFO market is very buoyant at the moment because the tech industry is doing well.
At least it's not a bad route for the thirsty 744 if the loads and yields are good, and I suspect both are, so it's minimising the negative impact of the fuel burn.
It's definitely a W and J heavy route - these classes are where the extra lift seems to be needed - so if a slot and aircraft were to be available, I'd guess the route could sustain a 772 3 or 4 times a week, especially during high season, without negatively affecting yields (because the 4 class 772 only has 120-odd Y seats).
Thanks,
Mike