The Book of Mormon frequently uses the phrase “in the borders.” For example:
And it came to pass that I did cause my people that they should gather themselves together at the land Desolation, to a city which was in the borders…
Mormon 3:5
This phrase also appears frequently in the King James Version of the Bible. For example:
And to the kings that were on the north of the mountains, and of the plains south of Chinneroth, and in the valley, and in the borders of Dor on the west,
Joshua 11.2
It is not a stretch to imagine someone appropriating this term from a frequent reading of the KJV.
I gave a study on this in a former ministry venue and your assertion is spot-on. The work ranges from improbable historical accounts to outright plagerism.
No doubt about it. I also think it involved automatic writing and spiritual assistance.