I'm not sure this is true. Encoding theorems in dependent types takes a lot of expertise.

Even without the Lean technical details, a lot of math theorems just don't mean anything to most people. For example, I have no idea what the Navier-Stokes theorem is saying. So, I would not be able to tell you if a Lean encoding of the theorem is correct. (Unless of course, it is trivially broken, since as assuming False.)

There is no "Navier-Stokes theorem". There is a famous class of open problems whether Navier-Stokes equations are well-posed (have solutions that don't explode in finite time) for various initial data, but that type of question is completely irrelevant for any practical purposes. I do share the feeling though. As a non-expert, I have no idea what the existing, allegedly practically relevant, formalizations of distributed algorithms actually guarantee.