For sure! I also wouldn't bet on a coin flip offered by a guy standing next to a 500-kg servo-driven coin-tossing machine. But their confidence in offering me

For sure! I also wouldn't bet on a coin flip offered by a guy standing next to a 500-kg servo-driven coin-tossing machine. But their confidence in offering me that bet is also useful information to update my probabilities. (This is also why poker is not purely a game of chance.) Probabilities are subjective, so we can always account for other people having more information and different probabilities than we do ourselves. Unfortunately the language of probability does not communicate this very explicitly, so it's easy to forget. With, say, radioactive decay, yes there's no chance anyone has less ignorance than we do, so we can at least be certain the result will be fair. (I don't think we are in any disagreement about this, though).