Not only is the article old, it contains no clinical data, only anecdotal from someone who switched from Purina to Blue Buffalo 5 weeks previously and now her dog was having loose, smelly stools.
Which could mean that the dog is sensitive to something in the food, or that the bag that the owner bought was stored improperly and had gone bad after being opened, or that the dog had been exposed to an actual illness like Parvo (loose smelly stools) or that the dog had ingested something which the owner didn't know about, or any of dozens of other things that cause dogs to have loose stools.
The statements from the Vets are general statements regarding food safety, not specific brands.