"Unique to the Book of Mormon" doesn't just mean "in the Book of Mormon but not in the Bible". Plenty of religious ideas, even ones considered Christian by many self-professed Christians, are not explicitly stated in the Bible. They've been around, though, since long before 1830.
The idea that the Fall was a necessary part of God's plan, for example, has been in the Roman Catholic liturgy for Easter Vigil since the 8th century.
O certe necessarium Adæ peccatum, quod Christi morte deletum est!
O felix culpa, quæ talem ac tantum meruit habere Redemptorem!
Oh so necessary sin of Adam, that was destroyed by Christ's death!
Oh happy fault, to have earned such a Redeemer!
This idea is no obscure thing pulled out of history, either. It was and has been prominent in Catholic worship and theology through the centuries even till now, and so it has also been well known and discussed in other Christian churches for centuries. By no means whatever is this a new idea from the Book of Mormon. I don't know when I first heard about "
felix culpa" as an idea, but it was when I was a kid, and whoever it was explained it to me mentioned the Latin term—not the Book of Mormon.
All the things mentioned in MG 2.0's list have likewise been well-known ideas since long before 1830. These are doctrines which one can perfectly well accept, if one so decides, without ever needing to learn them from the Book of Mormon. Indeed the fact that all these popular post-Biblical ideas appear in the Book of Mormon is one of the best reasons to conclude that the Book of Mormon is a product of the 19th century, and not some Biblical era. If nobody had ever guessed them until the Book of Mormon revealed them, then that might be an argument for the Book of Mormon being authentically different at least, but in fact the non-Biblical concepts in the Book of Mormon line up damningly well with the popular non-Biblical concepts in American society of Joseph Smith's time.
I was a teenager before it was cool.