Unknown option: --stop during migrate-import via Drush

Follow-up to #1800148: Unknown option: --rollback during migrate-import via Drush

drush help for migrate-import shows --stop as an option, but also complains that it isn't one.

$ drush help migrate-import
Perform one or more migration processes
...
Options:
...
 --stop  Stop specified migration(s) if applicable.
...

$ drush mi Article --limit="10 items" --rollback --stop
Unknown options: --limit, --rollback, --stop.  See `drush help migrate-stop` for available options. To suppress this error, add  [error]
the option --strict=0.
Unknown option: --stop.  See `drush help migrate-rollback` for available options. To suppress this error, add the option         [error]
--strict=0.

drush version 6.6-dev