Unable to close task assigned to me due to parent task

Unable to close task assigned to me due to parent task

Hello,

I'm unable to close a task assigned to me, the setup goes something like this:

Milestone
-Task list
--Parent task (owned by person A)
---Task (owned by person B)
---Task (owned by person B)

Person B cannot close the tasks assigned to him. It gives an error message "Task cannot be closed. Kindly close all parent task(s) for this task before closing this task."

I did not create the tasks, so I'm not even sure how a parent task was created in the first place. I find no mention of it in the Help files.

Is this a deliberate design decision or a bug? If this is a hierarchical design, then wouldn't it make more sense to require all child tasks be closed before closing the parent task?

Thanks