can someone please explain this for me?

SUMRX4 wrote:
...Also why would you calculate the weight of the axle itself into the payload? The axle weight is resting on the ground not the suspension. That one doesn't make sense to me.

They need to justify exceeding their ratings somehow; don't be interjecting common sense.
Your answer is, a conventional trailer has 10% - 15% tongue weight. A fifth wheel has 20% - 25% pin weight. Either way, tongue weight or pin weight goes against your payload rating. That is why you can pull a lot more conventional trailer then fifth wheel and still remain within your ratings.