Nephi concludes with the Gentiles. He has seen that the Gentiles will play an important role in the ultimate redemption of his own people, so it is easy to understand his charity towards them. If, as I have suggested, his own people included an influx of New World Gentiles, then this is yet another reason for the charity that he would feel toward the Gentiles as a category. Nevertheless, Nephi’s hopes for them are tempered with the caution that it is dependent upon the Gentiles acceptance of Christ.
For Nephi as a covenant Jew, he would make a distinction between the salvation through the Covenant and the Salvation through Christ. For the Gentiles, their access to salvation is only through Christ, not having part of the Covenant. Thus this caution is appropriately added to the Gentiles, but is absent from his statement of charity towards his own people and the Jews. While Nephi certainly understands that they also must eventually come to accept the Messiah, yet he understands them in a very different present relationship to God - one of the Covenant.