In copying from 𝓞 to 𝓟, Oliver Cowdery initially wrote “which are broken off ”. Perhaps he was influenced by the occurrence of “they which are upon the isles of the sea” in the preceding verse (2 Nephi 10:21). Or perhaps he had gotten used to the phraseology “are broken off ”, which occurred twice in 1 Nephi 21:1 as “all ye that are broken off ”. In any event, here in 2 Nephi 10:22 Oliver quickly corrected his error in 𝓟 by crossing out the are and supralinearly inserting have been (the level of ink flow is unchanged). Although 𝓞 is not extant here, it undoubtedly read the same as the corrected text in 𝓟, especially since either reading will work.
Summary: Accept in 2 Nephi 10:22 Oliver Cowdery’s change in 𝓟 of are to have been, an almost immediate correction to the probable reading of the original manuscript.