I think it's more about chaos: a deterministic system where the outcome is extremely sensitive to the initial conditions. Actual coin tosses function reasonably

I think it's more about chaos: a deterministic system where the outcome is extremely sensitive to the initial conditions. Actual coin tosses function reasonably well as random variables because most humans cannot control or measure the initial conditions of the toss well enough to determine the outcome before observing it. A computer model using a deterministic physics system would be completely aware of the initial conditions of each toss. You'd presumably want to introduce some randomness in those initial conditions (using e.g. a pseudorandom number generator) to simulate human coin tosses.