The main reason is that the TaskStatusManager.create_task_status() no longer supports passing in a *state*.  Per our discussion, the manager now ensures tasks are created with state=waiting.  This test (and some others) are creating tasks with specified state for testing and can no longer use the manager.  I added this function to mitigate the impact of the change to the manager on this test.  It seemed reasonable for a test case to have a helper function to do this.
As for side-steping coverage - IMHO, it's the responsibility of the task-status-manager unit tests to provide that test, not here.