This argument is slightly backwards. This is essentially the argument used for "javascript in the backend" and "let's package the whole browser as application runtime so we can use javascript". The core of the argument is that javascript is ipso facto the best language/runtime to write any code in, including refactoring existing codebases. Bringing javascript out of the browser also means you have to write bindings for javascript and recreate the existing ecosystems anyway.
Even if you approach this from "single codebase across runtimes" angle, the conclusion to bridge the gap between browsers and languages with existing codebase, expertise and ecosystems is much more reasonable than rewrite everything in javascript.