Josephus as the source for Luke's Jesus-as-child-genius narrative

Luke 2:42

And when he was twelve years old, they went up as usual for the festival [of Passover]....After three days they found him in the temple, sitting among the teachers, listening to them and asking them questions. And all who heard him were amazed at his understanding and his answers. 

Josephus' Life 1.2 8

 

I made mighty proficiency in the improvements of my learning, and appeared to have both a great memory and understanding. Moreover, when I was a child, and about fourteen years of age, I was commended by all for the love I had to learning; on which account the high priests and principal men of the city came then frequently to me together, in order to know my opinion about the accurate understanding of points of the law.