Yes, it's an issue with bind-mounted chroots. Even with the data moved, and the symlink in place, `unmount-chroot` does not unmount the chroot, as it expects the bind mounts to be in `/var/run/crouton/mnt/stateful_partition/crouton/...` (following the new symlink), but bind mounts are still in `/var/run/crouton/usr/local/chroots/...`.