Gibb, I wonder if you share my perceptions that

1. "Chanteying Aboard American Ships" isn't in finished form, despite its (welcome) book publication. The narrative part, IIRC, gives out midway through, to be followed by miscellaneous songs from all over.
2. Many of Harlow's texts seem "literary," in the Davis & Tozer tradition, as though he were trying to fill out or improve songs he'd partly forgotten.

3. Not all his versions are trustworthy.

It's easy for us trained researchers to underestimate non-scholars' innocently cavalier attitude toward their material. Harlow undoubtedly felt that any tinkering he may have done was not only harmless but beneficial. The words of chanteys varied anyway, right?

I see the book as more of an enthusiast's hodgepodge than as a careful (much less meticulous) record.