To answer one of your original questions, the reason it is an issue on the westbound but not the eatsbound is because of the way the winds blow. Flying West you're giong in to the wind, so the flight is longer/slower and burns more fuel. I've never heard anyone say that this flight is weight restricted at all. They load it to the gills pretty much every day when they can.

And as others have posted above, this flight does NOT divert for extra fuel as a matter of habit. I don't know where you got the other information from, but I don't think it is accurate.