Does this make any sence?

Every toy hauler I've looked at has the axles farther to the rear (5er and TT versions) opposed to their sister non-hauler (same length, brand, and manufacturer). Non-Haulers do have the axles forward more.

I'm sure every "hauler" comes with a weight limit for the garage area. This is to ensure the tongue weight does not decrease so much, the tail is too heavy, reducing weight on the hitch, causing bad towing conditions.

Move the axles farther back, and the hitch weight or tongue weight increases tremendously. It doesn't take much axle positioning to the rear to cause an excessive amount of hitch weight, that even a one ton would have problems with. So manufacturers have done the "math" to determine the best location for the axles with a recommended "do not exceed" wight for the garage to ensure good hitch weight and still be able to carry a load in the garage.

I went from a 38' KZ 5th wheel to a 38' Keystone toyhauler. The axles are definitely further to the rear on the toyhauler.

Moving the axles towards the rear increases the pin weight. This puts more weight on the truck which creates a different set of issues . It also changes the pivot point and maneuverability of the trailer.
18 wheelers are pulled by much larger trucks capable of towing 80K trailers. Totally different ball game than RV's.

Y'think that's bad ? (Not necessarily so)...how about the incredible rear overhang on some of the larger Class C motorhomes?

All the TH'S I have purchased TT and 5th wheels had the wheels towards the back compared to a regular RV. The engineering department probably designed them for best balance for truck and trailer. TH'S already have a high pin weight and increased pin weight would require a med duty or OTR truck to pull it, like a semi.

Numar mountaineer use to use duel's on there big 5th wheels.

If you have no weight in the garage, would that not make the tongue/pin weight super heavy?

so moving the tire set back is detrimental how? I'm not understanding this at all. My thinking is that it could carry more load weight wise in the rear..

Very likely that any added weight capacity would overwhelm the CCC of the unit or the frame would be out of balance / loaded in a bad way and you could have more failures.

They are balancing the capacity of the frame and the CCC of the unit with everything else on a giant sea saw that can have varied loads. The current placement is likely the safest and given the relatively low CCC of the units moving the wheels back further likely offers no benefit and perhaps could be detrimental.

Then again, maybe the guy that designed it is a jackass.