Truth is not the same thing as fact.
Facts about human history have since antiquity been preserved and transmitted by performance, art, and music. The modern Rice-Lloyd Webber opera, "Evita," is a perfect example. It's not just a powerful and moving production, it is a true story.
But the details are not always factual. And the narrative device is music. Almost every single word in sung. Does the fact that the story of Evita Peron is performed via the narrative device of opera make it any less true? Of course not. In fact were it not for "Evita" most people would never have learned of her.
A narrative device is a means to carry a point across. It isn't the same thing as a fabrication. For instance, in Luke 1.46, the Virgin Mary breaks out in song, the canticle known as the Magnificat. Did she literally sing this song in front of her cousin Elizabeth?
No. It is a narrative device because Luke wrote the first two chapters of his gospel not in Koine Greek, but in Jewish Greek, the type found in the more ancient Septuagint. He wrote his Infancy Narrative as a cantor's liturgical reading that people would hear chanted from the lectern on a Holy Day at the synagogue. Why? Because only the inspire dhistory of the Jews ever got this kind of treatment. Luke did this throughout the first two chapters because he believed the birth of Christ was a continuation of this history.
It did 't really occur in song or in Septuagint Greek, but like a film maker using black-and-white as means to show that something is historical before switching to color to mean we are in the present, Luke employed a writing technique to teach a point.
The point of the Genesis story is not that G-d caused a literal famine (G-d might have), but that G-d was saving people from disaster through Joseph. In Hebrew idiom of the time both good and evil were ascribed to G-d, so it is not clear whether the writer was being literal or merely employing idiom about G-d being the true cause of this particular famine.
In ancient Jewish writing, when an author skipped details or even made the details impossible to reconcile with reality, it was a narrative device that meant: "The details or setting is irrelevant to the story."
The important details of the story are the facts that Joseph is given the ability to interpret dreams and that this elevates Joseph into a position to save the lives of his family, preserving the seed of Abraham. In the end that is all that is important.
Was it really a dream about cows and grain? Exactly what are the details of the famine and why was on,y the storing of grain sufficient? We can hypothesize all day if we want, but the Bible writer breezes past these details. That is generally the ancient earmark to move along. It is just a technique of writing. It doesn't mean the device is false or true, it just means it is a device, a manner of telling a story.
This goes for the words "mythos," "mythology," and "legend." Legends are generally real. American history, for example, is transmitted mostly by legend ( like George Washington chopping down a cherry tree or Paul Revere's midnight ride). Legends aren't the factual story, but they are used to transmit truths.
Even when details are fictionalized, these fictional devices don't make the story false. Just because Evita Person didn't really sing "Don't Cry For Me Argentina" doesn't mean the haitorical person didn't feel such things or proclaim them over her very brief life.
The Bible is not a collection of news stories. It is a collection of religious explanations. Like he parables of Jesus, the stories themselves are not always factual, but the lessons are intended to transmit truths.