The title is a document attribute that in many cases can give clues about the subject matter of the document.
However, even with titles that are fairly descriptive the indexer needs to make decisions that reach beyond the document and the title
So, even if the title of the book is fairly precise, as in this case, the indexer is only provided with a clue, not the actual subject matter.
The indexer will have to make a decision about the actual representation of the document based on more than the information gathered from the title.