Supporting reference for Serial Number for Expense Items

Summary:

Want to use supporting reference of 'Serial Number' for Cost Management transactions (Ex: Event Class: PO Delivery into Inventory, Sales Order Issue) to pull serial number on all items, including expense items which are serialized, tracked on-hand, costed but are expense valuation.

When transacting items (Ex: Receipts, Sales Order Issue), see the asset valuation items pulling their serial number into the Supporting Reference for Serial Number, but expense valuation items are not pulling their serial number even though they are serialized and serial numbers have been recorded against them like the asset items.

Why is the serial supporting reference behavior different when its pulling from the same field for asset and expense items?