While that might be the case, I wouldn’t be surprised if they let teams play with k8s as well. Besides, one should always look at these choices objectively; if Google + k8s is a better deal overall than AWS & Mesos, then you shouldnt let your earlier investments cloud your judgement.
I know both Kubernetes and Mesos quite well. To be frank, they're on two different levels - and I assume the smart(er than me) guys at Netflix know that as well.