The structure of the documenation
Each of us have different path to learn the same stuff. It is impossible to order topics in ideal way. Different people care different topics at first. To deal with that, we provide a short list of topics everyone has to start with. Later each users chooses its own path to learn new topics. At that time alphabetical order is the best.
Nesting (topic tree) is evil. I say so, because given the same list of topics, each of us would create completely different tree. That means when you look for something, you have to guess where the author has placed the information you are looking for. So we avoid topic nesting everywhere where it is possible. Only three topics have subtopics: Classes, Functions, Form Object.
"See Also" section at the bottom of each topic completely removes the need of nesting.