Thank you for the update and for outlining the issue so clearly.
This behavior is expected and indicates that the webhook is functioning correctly. When a customer is redirected to the payment gateway, the system first creates the order with an unpaid (pending) status. At this stage, the initial order confirmation email is triggered, which is why the seller receives an email showing the order as unpaid.
Once the payment is successfully completed, the payment gateway notifies the system via the webhook. The order status is then updated to paid, and a second email is sent reflecting the successful payment.
If receiving two emails causes confusion, you may disable the order creation (unpaid/pending) email notification and keep only the payment confirmation (paid order) email enabled. This ensures that the seller is notified only after the payment has been successfully completed.