Why can't I detail my sales order reservation to the project and task level?

To detail the reservation to the project and task level, the incoming supply should have a project reference. You can reserve a project-based demand to supply without a project reference when the Allow Use of Common Suppliers option is set to null or Yes for an item on the item definition.

The reservation isn't detailed to the project and task when the incoming supply without project reference is received through a purchase order or transfer order, or completed using a work order.