The Patheos data is just reporting people who self-identify as atheists when asked about their religion. Many of them could also identify as "Non religious" or "Unaffiliated" or "None" when asked the same question (or not answer at all).

Errrr.....

Tell me, what is the difference, to you, between atheist and 'none' or 'non-religious'?

According to the Statista data, it seems that there are about 15.6% of prisoners that have no religious preference or didn't answer the question. That's roughly in line with the 22.8% of Americans who are unaffiliated according to the latest Pew survey.

Actually, it statistically considerably different, as you noted above. Nor does this change the other data noted earlier.

The claim that atheists are hundreds of times less likely to rape and murder than Christians seems wildly implausible, and is not supported by this data.

A high correlation is indeed supported by the data. As there are only .01 - .07 % of the prison population that are atheists (far lower than in the general population).

Now, if some other factor or factors in combination lead to both theism and crime, that still does not change the observed fact of this correlation. In fact, it would be wonderful to identify and hopefully eliminate these factors to prevent crime and allow people to not think mythology is real, which has its own demonstrable very unfortunate consequences.