This doesn't seem the same. In Counterfactual Mugging, my reward depends on my hypothetical behaviour in the counterfactual scenario. Here, you have explicitly ruled out that the counterfactual me can influence something.

Suppose a reward $1000 for passing the test. Let's also assume 100 copies of some person taking the test. If the copies are the sort of people who agree with the calculator no matter what Omega says, 99 of them would obtain $1000, for trivial reasons, and one gets nothing. This justifies the 99% confidence.

Even if Omega rewrote the answers of actual copies based on decision of other actual copies (I don't think this follows from the description of the problem), still it would be better to stick with the calculator. If the copies knew specifically that Omega appears only to those copies who have received wrong answer from the calculator, only then would another strategy become justified, but again for trivial reasons.

What am I doing wrong?