Nephi's brethren clearly do not have the clarity of understanding of the scriptures that Nephi did. While Nephi's use of Isaiah indicates that he had a natural and intimate understanding of Isaiah, that understanding was not shared by his brethren. In that, we of the modern world fully understand the plight of these who are our "brethren" in at least this facet - that we too have difficulty understanding the words of Isaiah.
In this case, Nephi is asked an interesting question. Are the things discussed in these verses literal or figurative. Will they really happen, or is this referring to just spiritual wanderings?