In the text, we read, "Behold, because thou didst graft in the branches of the wild olive tree they have nourished the roots, that they are alive and they have not perished," and hence the master could see the tree was "good."
According to Wilford Hess, "It would also have been unusual for an olive grower to graft wild branches onto a tame tree, … but circumstances exist when it makes good sense to do so. Due to the vigor and disease resistance of certain wild species, grafting wild stock onto a tame tree can strengthen and revitalize a distressed plant."
Hess states, "Knowing that it was highly unusual to graft wild branches into a domesticated tree teaches about the extent and effort the Lord makes to reclaim His lost children."
Wilford M. Hess, Daniel J. Fairbanks, John W. Welch, and Jonathan K. Driggs, "Botanical Aspects of Olive Culture Relevant to Jacob 5," in The Allegory of the Olive Tree: The Olive, the Bible, and Jacob 5, ed. Stephen D. Ricks and John W. Welch (Provo and Salt Lake City, UT: FARMS and Deseret Book, 1994), 484–561.
Book of Mormon Central, "Why Did Zenos Give So Many Details About Raising Good Olives? (Jacob 5:9–10)," KnoWhy 71 (April 5, 2016).