Here Oliver Cowdery’s correction in the printer’s manuscript seems to be a virtually immediate correction based on the original manuscript (no longer extant here), especially since the ink flow is the same. The as also seems necessary. And as we might suspect, other passages in the text have this same kind of construction, namely “as many as”:
Summary: Retain in the Words of Mormon 1:4 Oliver Cowdery’s nearly immediate correction in 𝓟 where he inserted the second as in “as many things as have been prophesied” (undoubtedly the original reading in 𝓞, no longer extant here).