I think people sometimes takes recruiters words too literally, wanting proficient in a language is a good way to scare of people afraid of leaving their box (I've met plenty of developers reluctant to try new languages and technologies).
Talking from personal experience I've rarely ever been more than slightly familiar with the language /required/ for a job and I've always made this clear however I've also explained that this isn't really a problem and I've never been rejected from a position because I weren't familiar with their arbitrarily chosen technology stack.
Quickly acquiring new knowledge needed for the job is the most defining quality for engineers/developers.
Talking from personal experience I've rarely ever been more than slightly familiar with the language /required/ for a job and I've always made this clear however I've also explained that this isn't really a problem and I've never been rejected from a position because I weren't familiar with their arbitrarily chosen technology stack.
Quickly acquiring new knowledge needed for the job is the most defining quality for engineers/developers.