This isn't turning the problem around in the same sense. In order to effectively turn a problem around you need to use its complement, and then it should be a b

This isn't turning the problem around in the same sense. In order to effectively turn a problem around you need to use its complement, and then it should be a binary proposition. Your example where you suppose an idealogical attack fails here because it is not the only other explanation, you haven't turned the problem around in the same way that turning "what is the probability this action had an effect" around can become "what is the probability that this action had no effect".