The article mentions that the trait is observable at only 4 weeks old. It might not be crazy to think that Humans are more likely to select the puppies that demonstrate the trait. It might not be "natural" selection, but if Humans are making a substantial amount of the breeding decisions for dogs then it could still be a form of evolution.

Indeed, selective breeding is sometimes called "artificial selection" as a mirror to the term "natural selection". Both are types of evolution.