Based on the tests with the Säker Ascension™ Harness and the Ruffwear Front Range® Harness, it seems that the Ascension is better at keeping your dog cool. Especially when looking at the profile view after the 1km walk.
However, when you check the Dog Pack Edition, the results are different. From the profile and top view, we can see that the Säker Ascension™ Dog Pack isn't as good as the Ruffwear Front Range® Day Pack to disperse heat.
One of the probable reason for that is that the sun wasn't hitting directly on the dog's skin when wearing the Front Range Day Pack.
Another possible reason for that is the color of each harness used in the test. The Ascension was black while the Ruffwear was red.
The goal of those tests was to determine whether the Säker Ascension™ Harness and the Säker Ascension™ Dog Pack would lead your dog to overheat due to the waterproof material.
These showed not only that this is not the case, but that in some configurations, the Säker Ascension™ Harness is better at keeping your dog cool than the Ruffwear Front Range® Harness (widely recognized as one of the best harnesses).