As the maintainer of Asciidoctor core, I can tell you that I honestly don't know. That probably says something about the feature :)
Joking aside, I've always been confused by the application of the verse table cell. It gives you preformatted (but not monospaced) text, just like a verse block, but there is no way to specify an attribution. I've yet to find a use case for this that I didn't solve by using an AsciiDoc table cell with a verse block. The only thing I can really think of is a mailing address or signature block. For that, you might want preformatted (but not monospaced) text and no attribution. But you could still solve it using an AsciiDoc table cell.
Long story short, it's really not something you'll ever see used.
Cheers,
-Dan