I disagree. If Odoo lets the user to create a layer at zero cost it should create also the journal entry with zero value. That is data consistency, the quantity in accounting for the product and the stock valuation account should match the quantity in the layers.

Not posting Journal Items with a debit or credit of $0 is by design - it has no effect on the General Ledger (won't affect any reports or calculations) so it just a wasted record.

If Material Receipts are using zero for the Unit Cost check:

That real-time Inventory Valuation is configured for the Product Category of every Product you want entries for.

That there is a product cost on the product, or if using Purchase Orders, that the Costing Method is average or real.

See https://www.odoo.com/documentation/user/13.0/inventory/management/reporting/inventory_valuation_config.html