Problem description
the explaination for using a remote docker volume makes use of the vieux/sshfs plugin
at the current time this plugin does not work under docker 18.09.7 build 2d0083d
Problem location
the explanation in question is at https://docs.docker.com/storage/volumes/#use-a-volume-driver
extra details
i have managed to reproduce the error by creating a docker volume and attempting to mounting an sshfs directory over the existing volume mountpoint