Could be all wrong here but I have pondered this axle weight rating thing for some time now and ........
It seems to me that not only is some of the trailer's weight supported by the hitch. Some of the weight of the unit is the wheels/tires and the axles themselves which are not technically supported by the axles. At least the way I see it. I'm thinking that it must be several hundred pounds.
But as I think more about it, the limiting component on the axle could be the bearing sets which do support the weight of the axles, but not the wheels/tires.
Does any of this make sense? Just thinking out loud and looking for a few more pounds of safety factor.
Now I'm really scratchin my head