We might be getting at a definition issue here. If a hidden meaning is so hidden that the author himself doesn't see it, is it then still a hidden meaning?
For me, for there to be a hidden meaning, the author must actively want to make a point.
Why?
Almost anything a person does reveals something about them, including unconscious biases and things they don't even realize about themselves. A work of fiction does the same thing. A work of fiction can provide insight or meaning never intended by the author, particularly when seen through the lens of time.