Similar to the Book of Mormon, the Book of Moses includes compound prepositions which would not be expected in English.
Mark J. Johnson explains:
Compound prepositions: Simple prepositions are words such as in, on, under, after, and around, that establish a relationship between a noun and a pronoun. Compound prepositions perform the same function, but with a combination of prepositions which act as a single word. Examples include on top of, in front of, or over against. Parry demonstrates one example from the Old Testament, “The Lord God of Israel hath dispossessed the Amorites from before his people Israel” (Judges 11:23, emphasis added). Moses 1:1 contains an example of a compound preposition, where “Moses was caught up into an exceeding high mountain.”– Mark J. Johnson – Book of Moses Essays #44: Moses 1: A Literary Masterpiece. Hebrew Literary Features of Moses 1 (Moses 1)
Why would Joseph Smith have included this if no-one noticed it in the Book of Mormon?