I am not aware of any code that enforces such login in Drone. The Kubernetes log stream can be found here: https://github.com/drone/drone-runtime/blob/master/engine/kube/kube.go#L238
Notice the code returns an io.ReadCloser from Kubernetes and then Drone performs an io.Copy that exits when the Kubernetes client closes the log stream. Would this imply Kubernetes does not close the io.ReadCloser until some output is written? If so, that would sound like a Kubernetes client bug?