@Xiang Fu, It seems that k8s has a new feature to use initContainer section to create sidecars. The feature is GA since k8s v1.33 but available since v1.28 and enabled by default since v1.29.
Since we Pinot helm chart exposed initContainers, I have adviced our team to use that, and there is no need to introduce a new sidecar section in the chart. I suggest to close this PR. I will write a comment in the PR as well.