Yes, type checkers are very good at tracking refactoring progress. If it turns out that you can proceed to test some subset, then congratulations, you found a new submodule.
I don't think it's a lack of curiosity from others. But it's more like fundamental lack of knowledge from you. Let's hear it. What is it are you actually talking about? Testing a subset of a library halfway though a refactor? How does a lack of types help with that?