The rear brakes have 2 ways of implementing a parking brake. One is a drum brake style that sits inside the "hat" of the rotor and uses the inside surface as the braking surface. The other is the style that Honda uses and it consist's of a mechanical linkage that allows the rear caliper to turn and "wedge" the piston like your always applying the brakes. You need to have the peg in the grove of the caliper piston in order for your parking brake to function properly and as seen here, allow proper braking on a normal basis. Common mistake even the best mechanic can overlook at times honestly.
I track my car pretty hard and experience this often, front and back. When I replaced my front pads 2 days ago the right front outer pad was at about 10% life and my rotor was smoking after one lap. The inner pad still had 40% life. Very weird. Happened to my rears as well, I can see the inner pad has more life
I could imagine that could happen if your really hard on your brakes for the day, normal day to day driving will vary 1-2mm difference between inner/outer pad wear. If the outer pad is excessively worn and the inside not touched then the pistons locked up and if the inner pad has all the wear then your slide pins are sticking/stuck.