Defaulting sub inventory rules are not defaulting shipping warehouse on child items of PTO items at

We have a PTO item that has make or buy items in the BOM The PTO is not expected to apply the default sub inventory rule but would expect the components of that item if set up with the default rules to apply the the sub inventory value example Item x - PTO Items Item Y - Purchased item with the sub inventory information set up Sale order line Order line 1.1 - Item X - No sub inv value Order line 1.2 - Item Y - sub inv value Currently the rule does not go down through the PTO