[kafka-extension] Tracing for Knative Eventing doesn't work

[sotatek-hungpham5]

Describe the bug
I tried to configure tracing for Kevent, include kafka-extension
The config is:

apiVersion: operator.knative.dev/v1beta1
kind: KnativeEventing
metadata:
  name: knative-eventing
  namespace: knative-eventing
spec:
  config-tracing:
          backend: "zipkin"
          # zipkin-endpoint: "http://zipkin.monitoring.svc.cluster.local:9411/api/v2/spans"
          zipkin-endpoint: "http://jaeger-collector.monitoring.svc.cluster.local:9411/api/v2/spans"
          sample-rate: "0.1"
          debug: "false"

Note that it's the same with Kserving
I've tested with imc broker and it worked well but cannot see anything related to kafka-extension in trace data, for both trace and metrics.

Expected behavior
Can see full trace of eventing application including Kafka extension.

Knative release version
1.15