It's less about being smart and more about having habits that fill in the gaps that a lack of static analysis leaves. This can happen through TDD or through REPL driven development. Each has their own strengths and weaknesses.
REPLs are super nice, TDD is super useful, but neither of them either preclude or obviate the advantages of static analysis. Although in practice, none of the popular statically typed languages has a standard REPL (except maybe TypeScript?) which is really a shame.
But I agree with you that it has nothing to do with smart vs. less smart.
On the other side of the coin, static typing doesn't catch a lot of things that TDD & REPL development can, although nothing prevents you from using tests with static typing.
No static typing advocates suggest that you shouldn't write unit tests - they just suggest that you can write dramatically fewer tedious but important tests that boil down to verifying type safety.
