Unable to active access logging in istio 1.12.1 with telemetry api

I have installed Istio 1.12.1 with helm on AWS EKS cluster 1.19
I have declared a telemetry configuration in istio-system namespace (root namespace) as shown here : Istio / Envoy Access Logs

apiVersion: telemetry.istio.io/v1alpha1
kind: Telemetry
  name: mesh-default
  namespace: istio-system
  - {}

But there is no access log shown in any envoy proxies.

Is there anything missing?

I managed to make it work by adding a property accessLogFile = /dev/stdout in istio configMap but there is no way to set this with Helm