Air dump/ rough ride

No you aren't completely wrong, they do say and I have seen, that your right rear tires will wear faster because more power or torque gets sent there.

However I am 100 percent certain that whichever tire has the least traction will spin first Everytime. Front or rear axle doesn't matter with power divider UNLOCKED.

 

Exactly right. There's THREE differentials in a tandem drive axle setup. Front, rear and interaxle. Unlocked, all 4 wheel ends will receive equal amounts of power at all times. Say it takes 400 lb-ft at each wheel end to power the truck forward. Now one wheel end loses traction and only require 50 lb-ft to spin. The remaining 3 wheel ends will get 50 lb-ft but since its not enough to move the truck, truck stays with a spinning wheel.

Now lock in the interaxle lock, power is now forced to go to the remaining axle as well. Torque to the wheel ends now equals whatever is needed to spin the wheels on that axle too.

 

Is the truck frame level front to rear with the bags inflated? If it has a slight rake to the front well there's your answer as to why the rear bags seem fuller.

 

One of the best videos if seen explaining how a differential works. And remember your truck has 3 of them

 

While there is air in the bags, most trucks look like the rear bags have more air in them, but the pressure is the same, now when you dump the air, every bag should go flat, if for some reason the rear is keeping air in them, it would sure spin the front axle, if the interlock is not locked in.