The API cannot access the data without importing data through the listings import tool. The data does not appear to be populated even though the data exists in the system. You can search for data using app's UI. You will find the data. For example, if you use the API to find an image URL, you will not find it. No image URLs are visible to the Inventory API.

Desired state is to have the API access to all products/inventory/listings and orders without having to import through the listings import.