Does this make any sence?

as most of the weight could or would be stored towards the rear of the RV?

Think of it this way. An 18,000 pound gross weight toy hauler might have a 4000 pound payload. That means the hauler weighs 14,000 pounds without the toys. Consequently, the toys are really not that huge of a load compared to the total weight of the toy hauler. Putting the axles all the way to the rear would create an excessive pin weight even with the weight of the toys as there is still 14,000 pounds of hauler weight that has to be carried somewhere. And, for most it is carried on the haulers axles. A 20-25 percent pin weight allows for a one ton pickup to be able to tow the hauler as only about 3600-4000 pounds of all the 18,000 pounds is on the hitch.