Product Upsell does checks to ensure that the user's cart qualifies for the offer before allowing customers to add a free product. However, it is not (and can never be) 100% foolproof due to the way Shopify accepts products. The app does offer a limit disclaimer function that should remove your obligation to ship products that the customer does not qualify to receive.
- Introducing "True Upsells" for Shopify
- Problem Solved: Creating upsell BOGO offers on Shopify
- How to use cross-sells and upsells to increase revenue on Shopify
- 9 upselling techniques to explode your average order value
- How to create simple upsells on Shopify
- Why upsells AFTER checkout on Shopify will be your highest converting click