That doesn't break the advantage, it just mitigates it. The advantage is just small enough that it doesn't matter much even before the mitigation. The caller co

That doesn't break the advantage, it just mitigates it. The advantage is just small enough that it doesn't matter much even before the mitigation. The caller could still look at the coin before it's flipped and have a slight edge in calling it. It's not terribly hard to influence the outcome of a die roll. You can roll it end over end like a wheel so two of the faces remain on the sides and can't be the result.