Confidence that the style performs best or confidence that the loosing ad is always going to under-perform? I'm not entirely sure either but I think confidence is related to each individual result. So, it's not a single confidence rating for the overall experiment e.g. we're confident in the results.
Winner and loser both have a result so you could be very confident that the looser actually was the worst version while only somewhat confident that the winner is definitely the best choice. It's kind of like saying, did the winner win because it's better or did the looser lose because it's worse? Which of these conclusions are we most confident in? That's my guess anyway.