Found out the hard way, but there is a “brake service” mode you can use to change the rear pads. It electronically disengages the parking brake so you don’t have to spin the piston flush with the caliper.
I removed the caliper completely because I couldn’t get the piston to recede. Lost all brake fluid to that caliper and now I’m waiting for a scan tool to clear codes just so I can bleed the brakes. I love the truck but it’s not easy to work on anything without getting error codes.