This dataset is definitely a treasure, and I love visualizing data. That said, i think what's missed when this is used as an argument for visual analysis is the idea of quantitatively identified outliers. If you take the descriptive statistics of p99, they most definitely will not be the same across these four sets. Visual analysis is a valuable dimension for data exploration, but it's a bit of a strawman to infer that "quantitative analysis could go no further, only visual analysis could figure this out"