Coin flips give legitimate 'could have done otherwise'

A fair coin flip is not random but determined by the position of every particle in the visible universe, yet it could have been otherwise in an important sense — its outcome is uncaused in that it has no salient cause — so we use coin flips to implement 'could have done otherwise' when needed; in a deterministic world some coin tosses are random (uncalibrated) and some aren't (a calibrated mercury-bath flipper always comes up heads), all without touching determinism.