My guess is that the previous set of pads were neglected and wore down to the rivets. This may have carved a groove into the surface of the rotor. Then the pads were replaced without replacing the worn rotor. After a couple thousand miles, the worn rotor carved the center out of the new pad, resulting in the odd-looking wear pattern.
Another thing that can cause weird brake wear, is if the sliders plates are corroded and allow the brake pad to get stuck or run slightly crooked. On the H3 front brakes, the slider plates are small stainless clips that snap into the calipers and the brake pads ride on them. These must be in good condition and lightly coated with caliper grease. I can see in your photo that they are bone dry. There is actually some rust on one of them, where there should be grease. Some premium pads come with new plates (PowerStop comes with new plates and grease), but most pad sets do not. I use EBC pads, and they do not come with new plates, so I buy them separately. Another trick I use is to run two springs on each caliper. GM only gives you one per side...but the holes are there so I run the second spring to keep things in alignment. This seems to help especially in muddy conditions.
The idea is that with proper lube on the sliders, and all the springs in place...the pads move evenly in and out and the springs keep the pads tight against the pistons. Without these tiny pieces...the pads are free to flop around and get hung up on the rough surface of the caliper casting. They often rattle when you hit bumps. You can buy the slider plates, anti-rattle springs, and caliper grease, separately at AutoZone. Without them...your new brakes will not perform properly.
BTW...Mjfarencak is missing the springs on his "Krylon Edition" calipers.
