IT's JUST A STORY!
Hosea 11:1- "When Israel was a child, I loved him, and out of Egypt I called my son."
So when I write my gospel, I will make sure to include that somehow.
Matthew 2:15- "where he stayed until the death of Herod. This fulfilled what the Lord had spoken through the prophet: 'Out of Egypt I called my Son.'"
So another story goes-
Exodus 12:46- In one house it shall be eaten; you shall not carry any of the flesh outside the house, nor shall you break one of its bones.
Numbers 9:12- They shall leave none of it until morning, nor break one of its bones. According to all the ordinances of the Passover they shall keep it.
Psalm 34:20- He guards all his bones; Not one of them is broken.
The Israelites probably had no idea why they could not break the bones of the lamb. But they avoided doing it because God said not to do it.
So when I write my gospel, I will make sure to include THAT somehow.
John 19:36- For these things were done, that the scripture should be fulfilled, A bone of him shall not be broken.
If the OT said something that made people believe that the messiah definitely would have some feature or backstory, then a writer in later centuries would certainly want to mention those features or backstory, whether or not the events happened or if the backstory is totally fictional.