The pickup trucks are also stouter than the 2500 Suburbans. You can think of them in three "tiers," relative to what was available in GMT800:
1) 1500 - half ton trucks, semifloater axles
2) 2500 SUVs - these are the equivalent of the 1500HD pickups of GMT800.
3) 2500HD pickups - even stouter, stiffer/higher-capacity rear springs, etc.
So just because the 2500HD pickup trailer rating goes up by 2500 lbs with the 4.10 rear, does not mean swapping in a 4.10 axle into an SUV would similarly increase its capacity. They're not the same platform.
Maybe the GMT800 2500 SUVs were more along the lines of the 1500HD pickup - especially because they didn't have the full floater axle, but the GMT900 2500 SUV from everything I can tell shares all the underpinnings of the 2500/3500 series pickup line
- the frame is good for at least 12,000 pounds , GM rated the GMT800 2500 SUV with the 8.1L gas engine at something like 12K for towing capacity, the GMT900 has this same exact frame.
- the front end components on the 2500 SUV are the same as the 2500/3500 series pickups
- the 10 bolt full floater axle on the GMT900 SUV - is the same as the pickups
- the 6.0L drivetrain is the same as the pickups
- the brakes on the 2500/3500 pickups - are the exact same parts as used on the 2500 SUV
- the 2500 series pickup with 3.73 gearing , is rated the same as the 2500 SUV - the only differences can be accounted for by looking at the different vehicle weights of each platform
Ergo................ a GMT900 2500 SUV with 4.10 gearing - should be fully capable of equal towing capacity to a 2500 series pickup with the same gearing.
There's absolutely nothing in the specs that points to anything that would make this not true. I've even gone so far as to look at individual part numbers on both platforms to see if there's any differences that might make the 2500 not capable. I can't find anything.