Std caliper o-ring seals are the only thing that causes brake pistons to move away from the rotors after use, plus of course any disc runout. When braking, the o-rings distort under hydraulic pressure. Brand new, the pistons only move about 0.010". I suppose really old o-rings would lose some resilency but I'd also expect to see fluid leaks as well if it was old o-rings.
The first time this came up, it was caused by seizure of the e-brake cables inside the cable jackets between the under-car bellcrank and rear calipers. Removal plus soaking in thin oil for a few days fixed the problem.
The second time (GT5-S), it was caused by having the parking brake on when someone undercoated the car.....It destroyed the tiny late e-brake pads within a few miles coming home. Both were OEM cables and 40+ years of weather seems more than enough time to rust such things once the plastic jacket cracks.