System mounts are handled as a special case in Kata. If there exists a bind mount for a system directory, we skip passing the host directory to the guest via 9p. This is done as it is not useful to share the host system directories with the guest. We instead mounted the guest system directory in the container rootfs.
This behaviour is useful as long as the source directory for the system directory is not a docker volume or a k8s host empty-dir.