We are looking into the best way to add native kubernetes support. Currently, you can add a mount on the host or directly mount the file system inside the container. Both approaches work well, so it mainly depends on your preferred architecture.
This makes it easy to declare the volume as part of the deployment and automatically attach storage when the container is run. Mounting on the host isn't very easy (or even possible sometimes), especially with spot/preemptible instances and the increasing abstractions by managed K8S providers. The pricing model might need to be different though if billing on a container-mount level.