[klibertp]

> but it seems that most of the changes were behind the scenes, and 1.17 largely didn't expose user-facing type errors or warnings.

That's how it normally goes with gradual type systems for existing languages, I think. The first step seems to be almost always adding a type checker that doesn't do anything in particular other than handling untyped code. Since being able to handle untyped code makes a type system gradual, announcing Elixir as "gradually typed" when this milestone is reached seems justified. After that, you're free to improve the type system and type checker(s), improve type inference, add specialized syntax, improve typed/untyped interactions, cover more language patterns, and so on. MyPy for Python also started without support for many things that were added later (and it's still being actively developed ten years later).