It seems to me that they made the same mistake that I did in my GitHub archive queries, they do not filter bot accounts. JavaScript, without filter, is on top 1 because of dependabot. If you filter all bots then Python is number 1, see: https://madnight.github.io/githut/#/pull_requests/2023/1
Wow, Nix is the most popular "functional" language! It is even more popular than rust
This is heavily carried by the Nix package manager's main package repository's (nixpkgs) development happening on GitHub. This isn't to say that Nixlang isn't popular, though. Anecdotally, I consume a lot of software that makes use of Nix.