I think, as a Bayesian, you're putting too much weight on your priors about the importance of IQ and are not interpreting the paper correctly. "Achievement" in

I think, as a Bayesian, you're putting too much weight on your priors about the importance of IQ and are not interpreting the paper correctly. "Achievement" in the context of the paper refers to scores on achievement tests, whereas the thing of actual interest is 'life outcome', and the analysis of that starts on page 3.