The scale approach can be level and split weight is still a problem.  A scale measures tension and if the entire vehicle is not on the platform, tension can be applied between the platform and the approach by applying trailer brakes and power to the drivers.

At one time there was a deal where an air bag was installed under the front of the fifth wheel so that the weight could be shifted from axle group to axle group.  Lift axles are also a concern.

"Where there is a will there is a way!"  And those who would cheat others will always look for an angle.  It was not uncommon for the counterweight on the balance bar scales to be weighted differently during full and empty weight.  My dad sold lambs private treaty over a scale for many years.  After he died, and when my brother sold most of the herd, we weighed lambs on an additional scale and there was something like a 8 lbs per head difference to the buyer advantage.  I commented on the crooked scale; then took my lighter lambs to the sale barn the following week.  My lambs weighed more than what my brother's scaled BUT the scale/feedlot owner was at the sale barn, sitting with the other buyers in a group.  I took a real hit on price.  Don't tell me everything was on the up and up.