Are you referring to the first figure, from Smith, et al, 2007? If so, I couldn't evaluate whether gwern's claim makes sense without reading that paper to get an idea of, e.g., sample size and how they control for false positives. I don't think it's self-evident from that figure alone.
One rule of thumb for interpreting (presumably Pearson) correlation coefficients is given in [0] and states that correlations with magnitude 0.3 or less are negligible, in which case most of the bins in that histogram correspond to cases that aren't considered meaningful.
Are you referring to the first figure, from Smith, et al, 2007? If so, I couldn't evaluate whether gwern's claim makes sense without reading that paper to get an idea of, e.g., sample size and how they control for false positives. I don't think it's self-evident from that figure alone.
One rule of thumb for interpreting (presumably Pearson) correlation coefficients is given in [0] and states that correlations with magnitude 0.3 or less are negligible, in which case most of the bins in that histogram correspond to cases that aren't considered meaningful.
[0]: https://pmc.ncbi.nlm.nih.gov/articles/PMC3576830/table/T1/