There are many things that might be different between a SRW and a dually of the same brand.
For instance the rear axle, tires, wheels brakes, springs. While some of those things may come from the same parts bins, meaning the same part numbers, some others may not. On your 2500 the wheels are definitely different. Same for the tires. Both of those things alone contribute to the lower rating.
I do not own a newer GM product, thankfully. But i did have an earlier version with a GVWR sticker of 9200 pounds. That truck loaded ready to travel scaled at 7500 pounds. Hitching my fiver to it the scaled weight jumped to 10,500 pounds. Pulling and stopping were never an issue. Handling in the mountains was an issue. It felt at times like the trailer was pushing me. Switched to a dually pulling the same fiver and the handling is as different as night and day.
Personally there is no way i would consider pulling a large toy hauler, or any large trailer for that matter without my dually.
