Jacob 5 is the longest chapter in the Book of Mormon and contains the allegory concerning the scattering and gathering of Israel. This chapter is well-known for being quite complicated and not easy to understand, however it is perfectly accurate in terms of olive culture and symbolism.
It also is consistent with other ancient parables and allegories from Near East, Greek, Egyptian and Israelite cultures.
Joseph Fielding Smith said of Jacob 5:
“But we have something in the Book of Mormon that, if we did not have other truth expressed in it, would be sufficient evidence of the divinity of this book. I have reference to the fifth chapter of Jacob…I think that as many as ninety-nine out of every hundred who read the Book of Mormon, read this parable through without grasping the fullness and meaning of it. And I think this is one of the greatest passages in the Book of Mormon…No matter how many times you have read the Book of Mormon,…take a few minutes at some convenient time and sit down and just read carefully every word in the fifth chapter of the Book of Jacob…No greater parable was ever recorded…I tell you, my brothers and sisters, Joseph Smith did not write it. That was written by the inspiration of the Almighty…When you read that chapter through if you cannot say in your soul, ‘this is absolutely a revelation from God,’ then there is something wrong with you.”– Answers to Gospel Questions, vol. 4, p. 203-7 as taken from Latter-day Commentary on the Book of Mormon compiled by K. Douglas Bassett, p. 183-4
Where would Joseph have learnt about olive horticulture and its symbolism related to the tribes of Israel? How could he manage to dictate Jacob 5 without getting lost in the storyline or contradicting himself?