When Oliver Cowdery copied this passage into the printer’s manuscript, he originally wrote “that he” after the complex parenthetical clause. Later, these two words were crossed out. The quill used for the crossout was considerably broader than the original quill that Oliver used to write the text; the ink appears to be darker, and the flow of ink was so heavy that the crossout ended up being badly smeared. It is difficult to determine who made the crossout, but it is clear that it is secondary. The grammatical motivation for deleting the “that he” is very strong. Before the parenthetical clause, the text reads “it must needs be expedient that Christ”, so the use of “that he” after the parenthetical clause is redundant. Yet “that he” serves the useful purpose of bringing the reader back to the original subject. The edited text is grammatically correct, but it is excessively complex and forces the reader to virtually reread the entire sentence to recover the subject. The earlier text thus permits an easier flowing text and definitely represents the original text.
The 1830 typesetter is probably responsible for omitting the redundant “that he” in the 1830 edition; and he may have been the one who actually crossed it out in the printer’s manuscript. The ink for this crossout is like the ink used in adding thus in the next line (see the discussion below for that variant). Multispectral imaging of the supralinearly inserted thus suggests that it was not Joseph Smith (in his editing for the 1837 edition) who was responsible for inserting the thus. From this we can deduce that Joseph did not cross out the “that he” either.
Interestingly, we have conclusive evidence that the 1830 typesetter later removed a similar redundancy after another parenthetical clause:
For Ether 9:8, the original manuscript is extant and agrees with what Oliver Cowdery originally copied into 𝓟 (that is, both 𝓞 and 𝓟 read “and he”). Just as in 2 Nephi 10:3, the redundant subject he and its preceding conjunction (and here in Ether 9:8) are crossed out. For Ether 9:8, we can be sure that it was the 1830 typesetter who crossed out the “and he” in 𝓟: the crossout is in pencil and matches the other pencil marks that he made on this page of the printer’s manuscript.
Summary: Despite its redundancy, restore the earliest reading in 2 Nephi 10:3 (“that he should come among the Jews”); the deletion of the “that he” is most probably the result of the 1830 typesetter attempting to eliminate the redundancy of the text.