I suspect this is a fairly new feature so you may get the first to try advantage.
My flights from LAX-NAN in June the business cabin was 20/24, but my flights NAN-AKL were 9/24. I think you may have to bid high on the LAX routes since everyone is trying to be up front for the long haul segments. Maybe check the loads on Expert Flier and guess based on how many seats are left for sale before you bid?