DD, I don't see anything about a "folkie" (or even "folky") sound in Lloyd's article. I do see a wish for more "vigorous," less "sentimental" and "precious" performances, along with a broader understanding of how shanties were actually used at sea. Such virtues wouldn't affect the generic style of presentation, however.

You may be more familiar with the development of twentieth-century musical styles in general than I am. But I'd be surprised if any of those early recordings featured any of the performance styles that nowadays might be considered "folk" or "trad" in any sense. I'm thinking of the simplicity of the early Burl Ives, the clamorousness of a banjo-player like Pete Seeger, the (mostly) unharmonized stridency of MacColl and Lloyd, etc. - much less the often gruff solos of authentic shantymen like Richard Maitland and Stan Hugill.

In terms of commercially released recordings, I'd guess those are all post-1930's developments.