I’m probably misunderstanding you or I’ve worded things in a confusing way that I haven’t noticed—I don’t think anywhere it’s implied what you do on Tails? The “iff” here is just saying you would be paid on Heads iff you would pay on Tails—the flip will happen regardless and the predictor hasn’t made any prediction about the coin itself, just you’re conditional behaviour
Edit: Maybe the “iff you will pay $1 on Tails” makes it sound like the predictor is predicting both the coin and your response, I’ll edit to make more clear
I’m probably misunderstanding you or I’ve worded things in a confusing way that I haven’t noticed—I don’t think anywhere it’s implied what you do on Tails? The “iff” here is just saying you would be paid on Heads iff you would pay on Tails—the flip will happen regardless and the predictor hasn’t made any prediction about the coin itself, just you’re conditional behaviour
Edit: Maybe the “iff you will pay $1 on Tails” makes it sound like the predictor is predicting both the coin and your response, I’ll edit to make more clear