In section 47 of his article, Re-vision-ing the Mormon Concept of Deity, Blake Ostler wrote the following which sheds much light on the “oneness” and “one God” texts in the Book of Mormon:
47. There is another compelling reason to reject the modalist interpretation of the Book of Mormon. It cannot be squared with other clear statements in the Book of Mormon, primarily in 3 Nephi, to the effect that the Son prayed to the Father, the Father sent the Son, the Son ascended to the Father and so forth. The culmination of the revelation of the relation between the Father and the Son is elucidated in 3 Nephi where the Son appears to the Nephites. As is appropriate given the inner logic of the Book of Mormon as a progressive revelation, the expression of oneness/threeness in 3 Nephi is much more clearly stated than in the prophets before Christ's self-revelation. The Book of Mormon presents the Nephites as not having fully understood the message of the prophets prior to Christ's appearance, and thus Christ undertakes to impart a fuller understanding to the Nephites. The inner logic of the Book of Mormon would suggest that as Israelites, the Nephites before Christs coming were concerned to preserve monotheism as understood in the Old Testament.21 Thus, the Nephite prophets prior to Christ's resurrection emphasized the unity of the Father and the Son. After the post-resurrection appearance of the Son, however, the plurality of the divine persons is much more prominent. Thus, Moroni can speak of praying to the Father in the name of "the Holy Child" (Moroni 8:3) and of the Son ascending to heaven to sit on the right hand of the Father. (Moroni 7:27; 9:26)
Note 21 for the above section readers as follows:
This seems to be Amulek's concern in responding to Zeezrom's question as to whether there is more than one God in light of the fact that there is both the Father and the Son. (Alma 11:28-35) Amulek's answer is "no," there is not more than one God. Such an answer is completely accurate from the perspective of Social Trinitarianism, but needs further explanation. However, the further explanation is provided in the text itself. In response to the question, "is the Son of God the very Eternal Father?," Amulek answers: "Yea, he is the very Eternal Father of heaven and of earth ... and he shall come into the world to the redeem his people...." (Alma 11:38-39) Thus, the Son is not merely identical to the Father; rather, he is the Father in a particular sense of sharing the creative and redemptive power. Amulek further explains that all persons will be judged before the bar "of Christ the Son, and God the Father, and the Holy Spirit, which is one Eternal God." (Alma 11:44) Thus, the oneness is a relationship of the Father, Son and Holy Ghost as one God, and not of the Son simpliciter.
