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The standard, official documents of the Lutheran church are contained in the book of Concord (https://bookofconcord.org/solid-declaration/election/).
In Article XI, on Election, in the opening paragraphs, the authors labor to show that God's choosing is in one direction: God chooses people to go to heaven purely out his grace (undeserved love). I'm writing this to confirm what you've already stated. In the paragraphs which follow the authors answer your question (¶75-85). I highly recommend reading through that entire article in detail.
Now, having shared with you that vital resource and summarizing it, let's look at some of what they write:
Are they speaking about someone who "utterly rejects Christ? Yes. Are they speaking about someone who is caught up in a habitual sin that eventually destroys their faith in Jesus? Yes. As a sample of the context consider this quote:
The reason why not all who hear the Word believe it (and thus receive the greater damnation) is not that God has not allowed them to be saved. Instead, it is their own fault, for they heard the Word not so that they might learn from it but only to despise, revile, and ridicule it; and they resisted the Holy Spirit, who wanted to work in them through the Word, as happened at Christ’s time with the Pharisees and their adherents [Matt. 23:26–36; Luke 11:37–54; John 7:48; 8:13; 9:16, 41; 12:42].Robert Kolb and Timothy J. Wengert, eds. The Book of Concord: The Confessions of the Evangelical Lutheran Church. Accordance electronic ed. (Minneapolis: Fortress Press, 2000), 653.
The result of the rejection of Jesus is apostasy. In fact, for the sake of the article, the two words are synonymous. Rejection is to thow something back and away. Apostasy (from ⲁⲫⲓⲥⲧⲏⲙⲓ) means to stand away from [Jesus].