Don't we still need someone to tell us what it is that may cause the brake pads to move away from the disks when, parked against the chocks, we let the brakes off? Same for a car's brakes. Could it be the relaxation of the O ring seals (usually square) slightly retracting their pistons?
Once did a max brake stop with a heavy on Boscombe Down's wetted runway from a speed calculated to cause the brake units to reach maximum designed energy absorption. Antiskids were Maxarets. An exciting ride!
A couple of tyres blew at low speed and much smoke as we ground to a stop. Disks were thick copper plated with hard chrome. Disassembled brake units looked terrible but they passed the test. Don't recall the final disk temperature nor whether the brake units were reuseable.