setting discount in appSubscriptionCreate does not work

[apps-developer]

hi, I have some issue when using discount on appSubscriptionCreate mutation. So I add discount as such in lineItems and I do not use durationLimitInIntervals because I want discount to be forver: 

lineItems: [{
          plan: {
            appRecurringPricingDetails: {
              discount: {
                value: {
                  percentage: 0.2
                }
              }, 
              price: { 
                amount: ${price},
                currencyCode: ${currency}
              },
              interval: "EVERY_30_DAYS"
            }   
          }
        }]

and it is all good for that particular payment it is discounted (in confirmationUrl) but when I check webhook payload which I receive from Shopify - it does not have the discount. The lineItems are without discount. O Shopify, I see that the next bill is set be without discount as well, see screenshots below. This seems like bug in Shopify. The subscription is created successfully but it does not have discount. Please help me with this cause it is a blocker.