At least some features, yes, and also some optimizations.

José Valim was the one who added "Add {continue, Term} and handle_continue/2 to gen_server" - https://github.com/erlang/otp/commit/69e009e3e1ad899a4609ff3...

José's contributions are at https://github.com/erlang/otp/commits?author=josevalim and Michał Muskała's at https://github.com/erlang/otp/commits?author=michalmuskala - there may be other Elixir devs in https://github.com/erlang/otp/graphs/contributors. (I even got in a tiny optimization myself once: https://github.com/erlang/otp/commit/07b0f4315b079cce7aeef7b...)