Why would Joseph Smith think to say Nephi had a tower in his garden?

Helaman 7:10 describes quite specifically the location of Nephi’s garden tower:

And behold, now it came to pass that it was upon a tower, which was in the garden of Nephi, which was by the highway which led to the chief market, which was in the city of Zarahemla; therefore, Nephi had bowed himself upon the tower which was in his garden, which tower was also near unto the garden gate by which led the highway.

Why would Joseph Smith say Nephi had a “tower” in his garden? Brant A. Gardner explains:

Nephi’s tower was almost certainly one of the many low pyramidal structures that archaeologists have found in the majority of Mesoamerican sites from Book of Mormon times on. Those attached to private compounds were lower than the stepped pyramids in public squares used for public rituals, but they were nevertheless similarly constructed, if not nearly so high. Nephi’s tower was low enough to allow easy conversation with the crowd (Hel. 7:12–13). In a family compound, such towers would have been suitable for prayer and communion with God.
– Brant A. Gardner, Second Witness: Analytic and Contextual Commentary on the Book of Mormon, 6 vols. (Salt Lake City, UT: Greg Kofford Books, 2007) 5:121

Wouldn’t Joseph Smith have thought it odd to include a “tower” in Nephi’s garden?

See:

Evidence Central – Book of Mormon Evidence: Nephi’s Garden and Tower

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