This behavior has been changed in EP.NET recently - in earlier versions a parent task could have a start date which was earlier than a start date of its subtask (there was no binding to subtask's start date, but only to end date), but now a parent task will always follow the date range of its subtasks - i.e. it will start on earliest subtask's start date and finish on latest subtask's end date (both start and end dates are bound).