It is an 'indicator' as to how much it can haul, although it is not meant to directly mean it can haul 1/2 of a ton. Since a specific weight model can be configured differently, you have to take the gross vehicle weight of the specific vehicle (the maximum the tire spring combo can handle), and subtract the empty vehicle weight.
As you go up from 1/2 ton, to 3/4 ton, to 1 ton ....you will find changes to tires and their load capacity, changes to the wheels (5, 6, 8 bolt), changes to springs and their capacity, changes to brakes and their capacity, changes to axles and their capacity, changes to the rear differential axle ratio, and even engine/tranny/frame/and cooling changes.
You can take a 3/4 ton frame, and based upon how it was configured/ordered, substantially change it's gross vehicle rating. Different manufactures have different capabilities, so you really have to sit down and almost compare line item to line item.
You can also have overlapping gross vehicle weightings, where you can configure a 1/2 ton frame (configured heavy), to have higher GVR than a 3/4 ton frame (configured light).