Previous istio proxyv2:1.7.5 is used with Prometheus with istio 1.8.x

Policies and Telemetry
1

Provision Istio certificates for Prometheus is by injecting a sidecar which will rotate SDS certificates and output them to a volume that can be shared with Prometheus as described here : Istio / Prometheus

Pod level annotaions:
spec:
  template:
    metadata:
      annotations:
        sidecar.istio.io/inject: "true"
        traffic.sidecar.istio.io/includeInboundPorts: ""   # do not intercept any inbound ports
        traffic.sidecar.istio.io/includeOutboundIPRanges: ""  # do not intercept any outbound traffic
        proxy.istio.io/config: |  # configure an env variable `OUTPUT_CERTS` to write certificates to the given folder
....

Above works fine with Pods running in strict mTLS enabled namespace.

But the added istio-proxy to the prometheus-server pod uses the image: docker.io/istio/proxyv2:1.7.5
Why is this the case ? Is hard coded or some other reason ?

Adding below annotation also not work:
sidecar.istio.io/proxyImage: docker.io/istio/proxyv2:1.8.2