We have the Stripe for Invoices integration with Avalara Avatax and our orders are not calling out to Avalara Avatax. Neither are the refunds for said orders.
This is expected behavior and is functioning as designed.
The Avalara system works fine in the subscription model in Stripe but if you are offering products to be ordered and purchased then you should expect Avalara to be unable to process the refunds.
Orders/ order events come under Stripe relay and the Stripe relay connector is handled and supported by Stripe