The writer says that Smith and Mormonism understood as concrete and material things that other Christians considered metaphorical or metaphysical. So God's body had to be physical and material. Heaven had to be a place with a spacial location or locations in our universe. "Holy garments" had to have an actual material equivalent. Religious community, authority, and responsibilities had to be more concretely described and instituted than they were in most other denominations.
I don't know how accurate he is, but it does explain many of the features of Mormonism that strike others as "strange" or "weird." Of course, 19th century Christians did tend to understand the Bible in a more literal sense than later Christians did.
Which ONE?
HE's got TWO; you know!!!