He has a slide-out and a generator on the driver's side of the coach. Even though the side to side leveling is through the rear axle, the front springs have to deal with the fact that the center of gravity of the bus is offset to the driver's side, hence higher weights.
Thanks, I figured that there would be a perfectly logical answer. If someone really cared about balance (or considering a bare bus), would the weights likely be more equal? I guess tanks would have a lot to do with it, too.