So, I messaged Vredestein about this & shared the photo above...
Here's their response (verbatim)
"This difference in width is normal. If you compare these tyre when they are mounted, the overall width is the same.
Because of a higher grip rating the tread of the Vredestein Ultrac Vorti is wider than the tread of the Vredestein Ultra Sessanta, witch better reflects its characteristics. "
I don't think I understand the response!