Sandburg says,

"In Southern work camps, John Henry is the strong man, or the ridiculous man, or any how the man worth talking about, having a myth character somewhat like that of Paul Bunyan in work gangs of the Big Woods of the North. He is related to John Hardy, as balladry goes, but with brighter bandannas. The harmonization is by Thorvald Otterstrom: it is massive in its pounding and evokes the atmosphere in which the powerful titan, John Henry, 'does his stuff.'"

I don't know if Sandburg included "John Henry" in his performances, but if he did it would have been the first time that most of his audience had ever heard of it.

The "ridiculous man" business is hard to explain, unless Sandburg is referring to some unprinted bawdy parody of the song or to some humorous folk tale.

Unfortunately Sandburg doesn't print any version of "John Hardy," who was also a steeldriver in some versions.