Mormon’s sentiment is obviously correct, that the gate of heaven is open unto all, but the reason that he highlights that particular piece of information in reference to this conversion episode is left unstated. If we return to our reading between the lines, it is probable that there were many who joined the church at this time who had been against it before. Certainly Mormon is not speaking of conversions from outside the Nephite territory. If these people had not joined before, they were certainly potential dissidents, if not dissidents in fact. Perhaps it is this fact that leads Mormon to point out the gospel is open. The conversion of those who had been enemies or potential enemies of the church would certainly demonstrate that the gate of heaven is open unto all.
It is also no mistake that Mormon emphasizes that this gate opens to those who confess the name of Jesus Christ, who is the Son of God. There is nothing in Mormon’s narrative that is more important that the testimony of this Messiah who would come, and at this point Mormon is moving rapidly to the time of the arrival of that Son of God among the Nephites.
Textual: In 1 Nephi 11:18 we saw the textual variant where the 1830 edition’s phrase “mother of God” was changed to “mother of the Son of God.” We have in this verse the same phrase “Son of God,” but this phrase is in the 1830 edition (the Original manuscript is not extant at this location, the lacuna beginning in our verse 21 of Helaman 3 and not picking up until Helaman 13. The Original Manuscript of the Book of Mormon. Ed. Royal Skousen. FARMS, 2001, p. 500-501).