Every study states it itself. There’s always a category for “unknown,” and if for some reason there isn’t such a category, you know the source you are reading is some full of shit organization that at best is misleading people just to collect money and at worst is only talking about dogs so they can push pseudo genetic science including eugenics and blood lible.
Your narrative from Wikipedia is some hysterical author focusing on one group of dogs. It’s also undeniable that training is an exponentially more significant factor in animal behavior than genetics, so let’s assume they were bred for fighting other dogs at a dog fight, so what? What does that have to do with dogs biting humans in their own homes or at the park? It’s a stupid argument you’re making.