Missing products in API endpoint product-warhouse

Hello everybody!
I am currently developing an interface from Shopware 6 to our ERP system. The inventory should be transferred from the ERP system to Shopware. However, these depend on which warehouse the products are assigned to.

I want to use the API endpoint “api/warehouse-product” to determine the products that are assigned to a specific warehouse. However, I only get the products that are assigned to the warehouse and that inventory was entered at least once.

Of course, this doesn’t work because the products in Shopware are assigned to a warehouse but do not yet have any stock (it comes from the ERP system).

Is there another way to determine the products per warehouse / warehouse group?