Yes we can make an argument incoherent by swapping words in and out. In this case the argument is not that a is evidence of b, it is that a ameliorates b. And

Yes we can make an argument incoherent by swapping words in and out. In this case the argument is not that a is evidence of b, it is that a ameliorates b. And that the risk of b is therefore priced differently where a is also present. So where a is not present, we must price the risk differently. How that assertion relates to the historical record may be of interest.