The author made one glaring mistake: basing "performance" on click through rates. What really matters on an ecommerce site is revenue. So which format resulted in a higher revenue? You'd be silly to make the assumption that greater click through = greater revenue.
Performance is based upon how well the conversion funnel performs. Revenue of course matters, but the way you get that revenue is to get people to go through the conversion funnel. What this A/B test shows, though crudely, is one optimization of one portion of the funnel. When you get more people to click on, say, a product page, you're "widening the funnel" at that particular point.
It's entirely possible to widen the funnel higher up, and still have the same amount of revenue; however, this doesn't mean that it was a useless optimization. Whenever you widen the funnel, you get the potential for higher revenue, especially with further optimizations. That makes for an increase in performance.
Lastly, widening the funnel at any point also means that you are getting increased page views, increased product views, and increased stickiness. That is _always_ a good thing, regardless of whether you increase your revenue or not. It means that people are more likely to interact, and buy from, your site in the future-- users are naturally more likely to go to a site that they know. So, greater click throughs to a product page, though you may not immediately see an effect, will almost always lead to greater revenue.