I understand. I don't disagree that this is how the Gregorian calendar currently defines these operations. The point is that this information is not useful or applicable outside of a very narrow and limited use-case, and therefore, does not warrant being exposed uniquely as general-purpose API because it is not general-purpose. Whereas, the operation that you define as
for all of its complexity, is the real-world behavior that most people need.
The Foundation Calendar APIs expose the complexity required to get correct answers; it is possible to get the results you want out of that same API, even if it's more verbose.