Ad Hoc tasks don't have the option to edit details
When you add tasks in My Work area without assigning it to any user/project (please see more details on how to create ad hoc tasks in the article https://support.workfront.com/hc/en-us/articles/216743198-Creating-Ad-Hoc-Tasks) you can't edit the planned completion date or other details on the task. The ad hoc task should not display any information other than name and description if it is assigned to yourself (a true personal task). In this case the commit date should always equal the planned completion date and the planned completion date should not be editable or viewable on the detail form.
If you assign another user to the ad hoc task it will start showing the details
When an ad hoc task is assigned to another user, they should see all of the standard task detail form including dates and the requestor and the new assignee should be able to edit the planned completion date independent of the commit date.