I finally found this writeup on the Zondervan Academic website. In short, the series titles are each authored by the scholars who penned the commentary. However, it appears that the "Themes" editions, while drawing upon the author's knowledge reflected in the commentary, are new works. They pull together themes in a synthesized, cogent manner. Just 15 were produced by Word, and the publisher was bought out by Thomas Nelson and later by ZA. ZA "discovered" these anew, determined that market forces that limited their success in the 90s were not present today and the volumes needed republished. They don't appear to be updated.

The Story Behind Word Biblical Themes | Zondervan Academic

of course, it appears, Logos disabled sharing links