What's happening here is that Apple is only producing, weakly, reference materials. There need to be at least three other kinds of documentation.
The one the author focuses on that's missing is the explanatory type. The sort that's discursive and provides a broader understanding of the whys and hows of the code.
Two other kinds of useful documentation that would complete the package are tutorials, of the sort aimed at programmers just starting out with the material, and how-to-guides, for programmers that have a general understanding of the material but could use examples and steps to accomplish a specific goal with the system.
The one the author focuses on that's missing is the explanatory type. The sort that's discursive and provides a broader understanding of the whys and hows of the code.
Two other kinds of useful documentation that would complete the package are tutorials, of the sort aimed at programmers just starting out with the material, and how-to-guides, for programmers that have a general understanding of the material but could use examples and steps to accomplish a specific goal with the system.