Now finally something which might make a little bit of sense.  

But I'm still not really buying it, though.  If that is the concern, it would make more sense to leave either the tractor or trailer brakes released, like you should do whenever split weighing a truck.  Dumping the air and letting the suspension collapse with the brakes set would cause the same problem as unloading and having it rise.   Finally, I have a hard time seeing a trailer being so weak that it can't handle the 'strain' of sliding an axle an inch or two.  An auger moving five or ten feet with the wheels captured I can see, but a traile has need of a lot stronger structure then an auger.  What happens when you try to move a fifth wheel?   

This looks like a good project to test.....I will set the trailer axle on the scale, lock all the brakes up all the way around, and see how much increase there is when I dump the tractor bags.   The load bars on our scale don't care which way the force is acting on them, so it should be easily measured.  I know that proper brake operation (leave the wheels which are on the scale, whichever ones they are, unlocked, lock the others to hold position) will make about 1000 lbs difference in the gross read when loaded.  If you just step on the brakes and hold them while you weigh we will show about 1000 lbs heavy, if you are careful it will weigh dead on.