The frame of reference to understand these is that they are targeted towards people that are unfamiliar with the preceding technology. The 'new' technology is obfuscated and hyped up in order to differentiate it.
They definitely used SaltStack - in the early days there was a bunch of Salt config in the k8s repo. I don't think it lasted long as it all got built around with k8s native infra/functionality.
Maybe... but that would only be because k8s comes out of Google Borg, not Ansible. Ansible wasn't even a thing when Google Borg was already in use at huge scale.