My example may or may not have a forecaster. The story doesn't say, and that's the point. Even if it turns out that the box is not forecasting anything, but simply making people do things, the winning move is the same.

The Smoking Lesion is used as a counterexample to evidential decision theory. But understood in the way that you just did, it would not be a counterexample. You have the desire to smoke. So you know you have that desire, and you already know that you likely have the lesion. So if you resist the desire, it does not become less probable that you have the lesion.

In order to be a counterexample, your estimate of the probability that you have the lesion has to change depending on whether you decide to smoke or not smoke. This is different from the situation that you just described.