Istio - load balance mesh internal HTTP2 traffic to non-standard port - kubernetes

Question

I want to load balance per request a mesh internal HTTP2 traffic coming to my ClusterIP Service over all its available replicas, using Istio; the first iteration is intended to work between two deployments within a single namespace, but I can't quite get there. I need to load balance on a non-standard port, I'm using standard port as a control group.
I was able to configure Istio so that requests from one long-lived connection to the service FQDN to standard port 80 are round robin'd correctly, but long-lived connection to a non-standard port such as 13080 will not round robin, instead a single pod will get all the requests (the behaviour looks like the K8s "iptables random" approach used in Service which only balances per connection, not per request).
Here's my most successful VirtualService definition yet:
apiVersion: networking.istio.io/v1alpha3
kind: VirtualService
metadata:
name: vs
namespace: example
spec:
gateways:
- mesh
hosts:
- "*.example.com"
http:
- match:
- authority:
regex: "(.*.)?pods.example.com(:80)?"
route:
- destination:
host: pods.example.svc.cluster.local
port:
number: 80
- match:
- authority:
regex: "(.*.)?pods.example.com:13080"
route:
- destination:
host: pods.example.svc.cluster.local
port:
number: 13080
Ports are defined in the Service like this:
- name: http2
port: 80
protocol: TCP
targetPort: 80
- name: http2-nonstd
port: 13080
protocol: TCP
targetPort: 13080
Using Istio 1.6.2. What am I missing?
EDIT: The original question had a typo in the VirtualService definition authority match for the port 13080 - there was exact instead of regex. Nothing changed, however. This supports the hypothesis that for some reason Istio ignores the non-standard port.