KubernetesPodOperator  pod_template_file content doesn't support jinja airflow template variables. pod_template_file  is part of templated_fields list. 
https://github.com/apache/airflow/blob/master/airflow/providers/cncf/kubernetes/operators/kubernetes_pod.py#L165

template_fields: Iterable[str] = (        'image',        'cmds',        'arguments',        'env_vars',        'labels',        'config_file',        'pod_template_file',    )

But pod_template_file content is not supporting template variables. pod_template_file can be implemented the way SparkKubernetesOperator implemented using template_ext

https://github.com/apache/airflow/blob/master/airflow/providers/cncf/kubernetes/operators/spark_kubernetes.py#L46
 template_ext = ('yaml', 'yml', 'json')
airflow/providers/cncf/kubernetes/operators/kubernetes_pod.py
"""
        Monitors a pod to completion that was created by a previous KubernetesPodOperator
        :param launcher: pod launcher that will manage launching and monitoring pods
        :param pod: podspec used to find pod using k8s API
        :return:
        """
        try:
            (final_state, result) = launcher.monitor_pod(pod, get_logs=self.get_logs)
        finally:
            if self.is_delete_operator_pod:
                launcher.delete_pod(pod)
        if final_state != State.SUCCESS:
            if self.log_events_on_failure:
                for event in launcher.read_pod_events(pod).items:
                    self.log.error("Pod Event: %s - %s", event.reason, event.message)
            self.patch_already_checked(self.pod)
            raise AirflowException(f'Pod returned a failure: {final_state}')
        return final_state, result
    def on_kill(self) -> None:
        if self.pod:
            pod: k8s.V1Pod = self.pod
            namespace = pod.metadata.namespace
            name = pod.metadata.name
            kwargs = {}
            if self.termination_grace_period is not None:
                kwargs = {"grace_period_seconds": self.termination_grace_period}
            self.client.delete_namespaced_pod(name=name, namespace=namespace, **kwargs)