Hi, and thanks for the question. Is it possible that one of the products is attached to a selling plan only via the variant? If so, that would explain why the count from your GraphQL query is less than the result you get from Liquid. The `sellingPlanGroupCount` on the product returns the count of selling plans directly connected to the product. Maybe you can try querying `productVariant` rather than `product`, if it fits your use case?
Let me know if you have any further questions.