There are inherent issues with task blocking which mean that it has
never worked properly. It is also very buggy and can lead to massive
performance issues with task processing.
It is almost impossible to deprecate this in a staged fashion because
various APIs use the methods and it is not possible to determine which
are API uses and which are other valid uses.
In reality there has been little-to-no uptake on the use of this feature
and it should just be removed.
Copy the CLI scripts from admin/tool/task/cli to admin/cli (schedule_task.php and adhoc_task.php)
and rename to scheduled_task.php and to improve in order to use cron_run_inner_scheduled_task.
dustinhuynh