Why do we have to enable Inventory Item Flag to YES for Items and associated SOs to show in SP?

Oracle Fusion Supply Chain Planning

version: 25A

My understanding was that setting up the planning method as MRP or MPS Planning is enough for the Item and associated sales orders to be collected in the supply plan, but it seems that we also have to set the Inventory Flag as YES. However, we have certain items for which we want to set the inventory item flag as NO.

One such scenario is the KIT Item scenario. We don't want to set the inventory flag to yes for the KIT item but it seems that this is required for the item and associated sales orders to appear in the SUPPLY PLAN.