I think the fact that it's lower on the number of posts indicates that there's less content about it, but people are more engaged (and posts more popular) when

I think the fact that it's lower on the number of posts indicates that there's less content about it, but people are more engaged (and posts more popular) when there is a story involving it. Also, as other commenters noted, this doesn't catch all stories (just the ones with a specific phrase) to minimize false positives. Although for OCaml, the false positives would be pretty rare.