That is absolutely true as well. We're porting a codebase to TypeScript and we were able to eliminate a bunch of test cases that were essentially testing type-correctness (e.g. can't pass a boolean to a date processing library). But those were bad tests to begin with, because there was no good reason for those tests to exist to begin with (we were pretty exhaustive with the invalid type checking even when the intended types were obvious).
Strict typing helps eliminate useless tests. And Rust types go further than most languages, such as exhaustive match, types that can exclude zero, and the near-complete lack of a null value.
If you're never going to publish the code, I agree, tests aren't necessarily helpful. Then again, I find writing tests helps me understand my own code better, so I still do it when doing research tasks (e.g. we were testing the potential performance benefits of porting an expensive algorithm to Rust, so my tests helped me benchmark it), though my tests are a lot less exhaustive and tend to be more happy path integration tests instead of proper unit tests.