It doesn't make sense, but that's exactly right. If their training sample had been only 4% gay and achieved 100% accuracy, then the true positive rate would be

It doesn't make sense, but that's exactly right. If their training sample had been only 4% gay and achieved 100% accuracy, then the true positive rate would be expected to be 1, because the denominator changes to 0.04. It does raise the question of how Bayes' rule applies if your sample is underrepresented, though... say their training set was only 2% gay. Could they achieve a true positive rate of 200%?