Changing brake fluid

That is not true. It doesn't leak, unless something is damaged.
Brake fluid is inside the caliper behind the seal. It doesn't leak past the seal unless the seal
and/or caliper wall are damaged or cracked.
The puck moves very little.

 

Not true. All rubber seals are wetted with a thin fluid film of lubricant for them to funcas designed. New caliper seals are assembled with a thin film of brake fluid.

Otherwise, heat will "glue" the lip of the seal to the metal piston.

It's like coating the rubber seal of the oil filter with a thin film of oil.