I noticed the same on my fronts when I did my first brake job on mine years ago. The inner pad on mine was thinner than the outer - dangerously thin, so tried to swap their positions ... like you could do for years and years on prior model year trucks. Of course, GM had to put a big block of metal on in the inner pad, preventing it from being moved! Was so pissed. Ended up cutting the pad so I could swap positions, just to get by until I had the time to replace the pads. Boy, I'll tell ya ...
I'm glad they went back to drums on the rear of mine. So much better than the "asshat" rotor/drum system for disc/ drum parking brakes. Up here in the northeast, those things are a CONSTANT pain in the ass. Always rusting out, seizing, and breaking, parking brake shoes delaminating, little retainer bolt busting off inside the axle assembly ... total horror show. With the drums, as long as you have the spring compressor for that large, single torsion spring, it's literally a 5 minute job per side to swap shoes.