pitr labels are not updated automatically on CR change and it's required to delete pitr deployment to see it.

Added labels in cr and applied it:

The label is not added after apply, because the deployment is not updated.

Deleting the deployment:

$ kubectl -n pxc delete deployment cluster1-pitr
deployment.apps "cluster1-pitr" deleted
$ kubectl -n pxc get pods --show-labels -l app.kubernetes.io/component=pitr
NAME                             READY   STATUS    RESTARTS   AGE   LABELS
cluster1-pitr-6f88567ccb-btmpx   1/1     Running   0          9s    app.kubernetes.io/component=pitr,app.kubernetes.io/instance=cluster1,app.kubernetes.io/managed-by=percona-xtradb-cluster-operator,app.kubernetes.io/name=percona-xtradb-cluster,app.kubernetes.io/part-of=percona-xtradb-cluster,mylabel=is-set,pod-template-hash=6f88567ccb