That's like saying the value of unit tests quickly diminish once you add non tested code to the mix. For fearless refactoring, sure, you need quite high type-c

That's like saying the value of unit tests quickly diminish once you add non tested code to the mix. For fearless refactoring, sure, you need quite high type-coverage to not get a false sense of security, but still, the more you have the safer it is. For just finding bugs and code navigation, any addition of types is going to be a win.