I expect developers to know more than one language, especially if one of them is Erlang/Elixir. It's not a stretch to expect a backend/fullstack dev to know Go, Javascript, and/or Python on top of Elixir. It would be more common for them to not know Elixir than the previous 3.
Also 50 LOC is small enough so there is not much complexity. Making that binary grow more than needed should not be validated during code review.
My use case is as follow: I need an implementation of the iCalendar RFC. The current Elixir implementation does not implement the full RFC, especially features that I need. Implementing this myself would be far more complex than 50 LOC in another language, relying on a fully implemented and well tested library.