This is Moroni’s essential task. While he is alive, he is “commanded… to write” and then hide up the record. Moroni declares that he has done that which was commanded of him. He has written, and he has sealed up the record of the brother of Jared, along with the interpreters that will be required for its interpretation.
The essential part of this particular insertion, however, comes with the information in verse 6; that “they shall not go forth unto the Gentiles until the day that they shall repent…” Moroni’s future-focus returns to the forefront of his writing, and hijacks his writing. Moroni shifts from discussing the events of the past to lecturing the people of the future. The discourse appears as the words of the Lord. Since Moroni surely did not take dictation when the Lord spoke these things to him, we are getting Moroni’s retelling of a personal experience. That experience looks to the future. Since it came from the Lord, Moroni associates his vision with the vision of the brother of Jared, and that allows the experience to become relevant as Moroni tells the story from the plates of Ether.