I rarely need to dig into the implementation details of a class but when I do, if the language gets in my way, that's probably a bad thing. People make mistakes

I rarely need to dig into the implementation details of a class but when I do, if the language gets in my way, that's probably a bad thing. People make mistakes in API design and strict API contracts as a feature of the language can be annoying. FWIW, I remember only one case of having to do #define private public in my 10+ year career when dealing with a third-party library. The point is that the API should be a strong suggestion, but not necessarily strongly enforced. The arguments you make apply equally to Python, btw.