>Eg last I checked Anthropics one-shot performance on Clojure was about the same as Python or Go despite almost certainly being less represented in training data. The combination of density and simple primitives might be easier for an LLM to wrangle, ameliorating the impact of a less popular language.

There might be tons of confounding factors there. One that comes to mind is the quality of of data, it might perfectly be that the average clojure snippet is higher quality, due to the users demographics. Very few people start writing code with clojure, whether in college or during bootcamps.