I agree, the locker should have nothing to do with the GVWR.
I misspoke and was wrong as I referenced a specific item that is likely a lesser aspect of the payload reduction. Sorry. It apparently is the "whole package" with the springs likely being the key contributor but the entire suspension as a whole that the "Rebel" does not have is in play for the reduction. Don't know what I was thinking when I wrote that.
"Its suspension was specifically designed (FCA’s RAM engineers threw millions of dollars at it) for this type of terrain by including Bilstein shocks, modified control arms, softer spring rates, more than two inches of lift, and Power Wagon’s exclusive
Articulink design. Articulink incorporates
high movement joints at the control-arm-to-axle mount, allowing for additional flexibility and extended axle articulation. Second, additional front-axle flex is possible with the driver-actuated “Smart Bar” disengagement. This front sway-bar disconnect is possible in both 4WD-High and Low transfer case gearing when traveling under 18 mph."
TFL notes "The suspension uses a single rate coil springs and tuning to provide very good off-road articulation and a comfortable on-road ride. There is a compromise, and it comes as a decreased payload and towing capacities."