USPS Ground Advantage Discount on Shopify Plus vs. Shopify Basic

[Ash33]

Hello,

We recently upgraded from Basic to Shopify Plus.

We understood that higher-level plans (above Basic) get higher shipping discounts up to 88% vs. 77%.

However, we are not seeing any difference in the USPS Ground Advantage Shipping costs.

Has anyone else experienced the same OR has anyone else seen a difference in shipping discounts between Basic & Plus for USPS Ground Advantage?

Thanks in advance