I have no idea what so ever, but if I were to hazard a guess, I would say it is just more pretense of understanding something one does not.
Since the foundation of language is yet unknown, and untaught, I would say that what metaphor really is is itself unknown. Certainly there are descriptions of aspects of it, but no knowledge.
Let me examplain how I understand metaphor, plain and simple.
Under the two element metaphysics, which degenerated into simple set theory, there are only two methods of constructing a set. Transform set into thing, and we have the definition of a thing. A thing is any material difference in some form. From this the binary assertion and denial is also abstracted.
A set can be constructed, or a thing constructed in two ways, enumeration and definition, ie. material difference and form.
Definition determines class membership. Every member of a class is a member of a class by the standard, the definition itself.
An example is the Biblical name of the Beast 666. Man has claimed it impossible to solve, however the answer is given at least 4 times in the text, that is how to arrange the numbers, simply use standard numeration.
"To make our coming and going so as to turn the past into the future and to bring the future to pass."
This particular metaphor requires two keys. It is a description of the function of the human mind itself--after all, the book is about judgment and uses principles of judgment to "seal" the text. It is a psychological demonstration.
Metaphor, called simile in multis by Plato, dark sayings in scripture, works it the other way around--given members of a set determine the common characteristic, i.e. the definition.
Thus a member of a class is used to refer to the class definition.
Thus, when one truly learns judgment, or logic, or languag itself, understanding is exercised through class mechanics which includes metaphor.
Metaphor is important because, apart from exercising judgment, it is used to construct myths that aid in the modification of human behavior by the manipulation of emotion. Religious mythology is an example. Properly constructed religious mythology through the use of metaphor actually translates into scientific fact. However, it takes advanced understanding in logic to reduce the metaphors back into statements of fact derived from original definitions.
Religous mythology is part of a complete understanding of psycholinguistics as understood by great minds such as Plato, and what ever had the Judeo-Christian scriptures compiled.