Ether was a descendant of a people who had left the Old World. While his people were not called Israel at that early date, they were still people who were covenanted with God. They had left the main body of the covenant people and come to a New World. Moroni was similarly a descendant of a remnant of the House of Israel that had left an old promised land for a new one.
The similarity of experience and history both explains why Ether receives this vision of the future, and why Moroni wants to record it. For both men, it is an affirmation that their separation will yet yield the same blessings from the Lord as the main body of his covenant people.
As Moroni retells the vision, he relates it to the scriptures with which he is familiar. The explanation of the type is again demonstrably Moroni’s, because Ether’s people left prior to the time of Joseph in Egypt. Moroni had the story through the brass plates. Ether could not have known it. Therefore, this method of explaining the meaning of Ether’s vision comes from Moroni, not Ether.
The type depends upon the fact that Joseph went Egypt and never returned. Although Israel eventually left Egypt and returned, Moroni ignores that part of the story, and concentrates on the separation that left Joseph in Egypt. The Jaredites and Lehites are therefore compared to Joseph who was separated, and became a powerful and righteous people in a foreign land.
After the comparison to the separation, Moroni tweaks the next phase. Where Moses leads Israel out of Egypt and symbolically to Jerusalem, The Jaredites and Lehites will also leave their “separation” and come into Jerusalem, but a New Jerusalem.