The DiscountExpression, which is a discount based on a formula defined in the promotion settings, always uses the cheaper freight option regardless of the shipping method selected by the customer. This results in discrepancies between the discount given and the expected discount based on the selected shipping method.

• Create a promotion formula that applies a discount based on the total amount including freight.
• Set multiple shipping methods with different costs.
• Add items to the cart and select a shipping method that is not the cheapest.
• Apply the promotion and proceed to checkout.
• Observe that the discount is calculated using the cheapest shipping method rather than the selected one.

There is no workaround available.