Anecdotally speaking, he hasn't been hands on with Oban[1], yet he still offers advice and guidance around the project because it is in the Elixir community.
But I agree Jose is always helpful and the strongest pillar in the community.
As the founder of the language, the lead evangelist, and the main mouthpiece, yes, 'single handedly' may be hyperbolic, but only slightly. It's not to dismiss others' inputs, but it is to highlight how -insanely- engaged he is. I can think of no other language founder who has put in nearly the same legwork.
I don't pay particularly close attention these days, but I'd think Rich Hickey's involvement in Clojure over time, at least to the point Elixir is today, would be comparable.