2021 GMC Sierra AT4 3500 here and I have had the truck since December and here are my thoughts so far.
I noticed the GMC Yukon has the rear view camera as well. So I would imagine the perspective on that camera would be more appropriate for the back of a truck cap than the current truck camera relocated to the back of the cap.
I know people were successful with relocating the existing truck camera to the truck cap, so if you swap that camera out with the Yukon camera then we might really have something.