Pod that return 503 are not called


I’m playing a bit around with Istio by using the Istio Tutorial from Red Hat. In the section Retry (https://redhat-developer-demos.github.io/istio-tutorial/istio-tutorial/1.1.x/5circuit-breaker.html#retry) it is shown Istio will not redirect requests to pods that replied previously with a HTTP status code 503. The test case contains no description why Istio is doing this and I can’t get my head around it. Could someone give me a hint, which feature of Istio could be used for this? What is also confusing for me that I Kiali is not showing any 503 error for the pod that returns 503 or at least this is how I interpret the result. Could somebody give me hint what the reason for this could be?

Thank you very much in advance,