In fact, it has been proven the opposite. 6.5L 1/2 tons did indeed come with different torsion bars.
You seem to have a different understanding of this all. You're saying that it is possible to do, and it won't break. Well, this is true. People put plows on the front of 1/2 tons all the time. But just because it can be done, and just because it won't break, doesn't mean it's the best approach to the situation, and doesn't mean it won't cause other issues. Like I previously stated, You can't change static weight, keep the same spring rate, and expect something to handle the same. If he's got the ability to change torsion bars, it would be beneficial to him. Sure, he can leave the ones that are in there, but it would be better if he were to change them.
I'm not trying to get into a d!ck swinging contest with you. But I tune suspension day in and day out. It's what I do. For 10 hours a day I weld, and for the other 6 I tune suspension. You've got a Duramax swapped GMT400? Cool! I've done a few engines swaps myself. You moderate a very small unpopular forum? Cool! I've administered literally millions.
The problem you're having is with perspective. You're looking at it as far as what is possible to do, and I'm looking at it as far as what is better to do. You can do a SAS without moving your axle forward. That's very possible to do. You can put a body lift on without extending your shift linkage. That's very possible to do. You can weld in patch panels without first having sprayed weldable primer on the back side. That's very possible to do. But none of them are the right thing to do.