why is the finish date of the work order not calculated by the lead time of the material attribute ？

Hello engineer, I have a question, please help answer it, thank you。

When manually creating a discrete task, enter the start time, the work order completion time is automatically calculated by the routing, and the start date and end date of the MRP work order are calculated by the lead time of the material attributes, why is the finish date of the work order not calculated by the lead time of the material attribute when the work order is manually created and the start date of the work order is entered?

Oracle E-Bussiness Suite.Manufacturing

Oracle Applications : 12.1.3