However, the filter query:“productType:shirt” returns nodes with productType different than “shirt”. I also tried this query in a live shop and had similar results. Is it possible to filter results with a query on productType or other fields?
You are querying on a field that doesn’t exist, hence why the results aren’t as expected. If you look at the documentation for the product query root, it specifies you can query on “product_type” not “productType”. See here for reference: https://shopify.dev/docs/admin-api/graphql/reference/queryroot
@Kevin_A Thanks for the clarification but the screenshot is directly from the Shopify documentation so I would recommend updating it to remove the wrong field reference