Does the 'run_in_parallel' config option work?

From my testing and after looking at the source code it does not seem that the 'run_in_parallel' task configuration option (as described here: https://github.com/openstack/rally/blob/master/doc/specs/implemented/new_rally_input_task_format.rst, and defined here: https://github.com/openstack/rally/blob/3.1.0/rally/common/objects/task.py#L57) is anything but a NOP at this point.

The configuration option does no seem to be read anywhere, and the comment in db/models.py indicates that the value is always false: https://github.com/openstack/rally/blob/3.1.0/rally/common/db/models.py#L177. Is my understanding correct?

I want to be able to simulate realistic cluster load and that requires running multiple scenarios in parallel. If this is indeed a NOP, are there any other ways to achieve this goal?