It's not so much that you may overload the axle rating (many here are over the posted axle limit)...it's the type of axle you will be overloading.
A semi float vs a full floater makes all the difference.
With an HD truck your axle limit reflects the tires/wheels. These can be ea$ily upgraded.
With a half tom truck your axle rating IS the axle. I don't think you could easily upgrade that.
All that does not mean you can't carry a TC on a half ton...you certainly can. But the weight becomes much more critical. You don't want to exceed the posted axle rating on a half ton.