We're trying to access the HS code ("Duties" array) via the Order object. It seems the HS code is available in the Inventory JSON, but not the Order JSON (?). It seems that the 2021-04 API docs indicate that the HS code should be available in the Order but we're not seeing the values populate.
The screenshot below is from the Shopify Developer Docs. It shows that the HS code should populate in the Order (API version 2021-04). Our Order json just shows an empty value for the "duties". All of the other values on the Order line_items json populate, but the "duties" value (which should include the HS code) is "duties":,