This is an unusual interjection into Nephi’s narrative. He ended the previous by having all of the brothers and Ishmael’s family return to the tent of his father. They are now all in the same place. That makes it logical that the event of gathering the grain and seeds might happen at this time, but it is unusual that Nephi tosses this sentence in without any context or any reason. Perhaps he was indicating that they would remain there for a while, but that doesn’t really appear to be the case. Right after this sentence, Nephi will begin to recount his father’s dream of the tree of life, and then give his own version of that vision. He will teach his brothers, but when that discussion is over, he will quickly have the brothers get married (1 Nephi 16:7).
Nephi will not tell us how much time passed, but Lehi receives another dream that they should depart further into the wilderness (1 Nephi 16:9). It is at that point that Nephi speaks of gathering their provisions, and seed of every kind (1 Nephi 16:11). This verse in Chapter 8 appears to belong to the story in 1 Nephi 16. Perhaps Nephi intended it here, or perhaps he skipped to that part of the story and realized that he had jumped ahead.
This does not appear to be a case of repetitive resumption. Not only is it a very long inclusion, but the inclusion covers both the visions and the discovery of the Liahona. I suggest that it is an innocuous error where Nephi jumped to the wrong story, and quickly got back to the intended outline.