I read the studies he cited and I'm not sure we can conclude anything from them. As far as I can tell, "bug density by language" is not a thing you can measure in a meaningful way. It depends on the specific programmers at a specific point in their career, their skill level, domain knowledge for the project, scope of project, who the project manager is, their culture of testing, etc. For example a great JavaScript programmer will make a less buggy program than a mediocre c++ programmer.

There is no silver bullet, though the article tries to pass off TDD as one. Also he does concede that static types can power tooling that might "feel like they make us more productive".

Disclaimer: I prefer having types but I also think JavaScript is great and don't shy away from using it.