Late Front Caliper Piston, Wont Compress Back In Options

[Costa05]

Back story. Car has not been driven for probably 20 years but getting close to getting back on the road again. These are late front calipers by the way. I removed the calipers to clean things up and put some new hardware and brake pads on. Picked up some almost new rotors those are good. Tried to compress the caliper pistons back in with the calipers removed from the car and would not budge using 6" C clamp and wood protector on piston (lots of force by the way). Figured they were frozen so I did the grease gun trick to try to force the pistons to move out which worked almost effortlessly (inner and outer piston). Before forcing them out all the way I tried to push them back in to get movement both ways and got nothing. Neither side will budge trying to compress them back in. Bleeders are removed. No brake lines attached to it at all. Thought I would get grease pushing as the pistons got forced went back in. I am stumped. How could they be frozen in one direction and not the other?