Re [1]: I think that's a reasonable statement. My issue with it, however, is that after just a few weeks (or even a few months), said developer might still not know about various design pitfalls or best practices in the new language.
In short, they might not be writing idiomatic code, and you'll end up maintaining it for a long time. IMHO, becoming basically proficient with a language is very different to being able to create software which will scale well to large teams, while also aging gracefully over time.
In short, they might not be writing idiomatic code, and you'll end up maintaining it for a long time. IMHO, becoming basically proficient with a language is very different to being able to create software which will scale well to large teams, while also aging gracefully over time.