I haven't hit their site yet, but I don't think they're saying you need Elixir to build this kind of project. I think it's more along the lines of needing Elixir to build a tutorial series for Elixir.

As for the benefits of using Elixir, I'm not qualified to answer that since I've only skimmed the surface of what Elixir is (but it looks intriguing!).