Bigger tool box compartment for panel truck.
My guess for Suburban shorter tool box riser is for easier access to rear seats.
In panel truck you enter rear floor board in 2 steps
Suburban gives you 3 steps to enter rear of vehicle.
Step 1 Ground to running board
Step 2 Running board to floor board
Step 3 Floor board to rear floor board
Carpenter lingo: Tread & Riser in stairway building.
