Why was one sixth of the 1830 Book of Mormon set from the original manuscript?

Evidence from the manuscripts of the Book of Mormon (as well as internal evidence within the Book of Mormon itself) shows that for one sixth of the text, from Helaman 13:17 to the end of Mormon, the 1830 edition of the Book of Mormon was set from the original (dictated) manuscript rather than from the printer’s manuscript. For five-sixths of the text, the 1830 edition was set from the printer’s manuscript, the copy prepared specifically for the 1830 typesetter to use as his copytext. The reason for the switch was the need to take the printer’s manuscript to Canada in February 1830 in order to secure the copyright of the Book of Mormon within the British realm. During the month or so that Oliver Cowdery and others were on their trip to nearby Canada with the printer’s manuscript, the 1830 typesetter used the original manuscript to set the type, although he himself was unaware that there had been a temporary switch in the manuscripts.