Yeah, slow as in brain power in mHz...........I NEVER bleed all 4 lines when pulling a caliper. If you block off end of disconnected line to not leak and quick enough doing it, the amount of fluid in master never gets low enough to expose air, the other 3 lines will still be full also. A simple 2 minute single line bleed and pedal solid as a rock in every case.
Odds heavily in favor of nothing wrong with master unless someone has now messed it up.
Sad how bad the Ford techs can be now, but same I guess as when we had a shop across the street from a GM dealership, we fixed LOTS of GM cars they couldn't figure out all through the '70s. They sure seem to have no trouble figuring out the highest priced part that 'goes bad' on your car though. Odd how that is the one that always seems to be at fault...............