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
pod_template = self.full_pod_spec
        else:
            pod_template = k8s.V1Pod(metadata=k8s.V1ObjectMeta(name="name"))
        pod = k8s.V1Pod(
            api_version="v1",
            kind="Pod",
            metadata=k8s.V1ObjectMeta(
                namespace=self.namespace,
                labels=self.labels,
                name=PodGenerator.make_unique_pod_id(self.name),
                annotations=self.annotations,
            ),
            spec=k8s.V1PodSpec(
                node_selector=self.node_selector,
                affinity=self.affinity,
                tolerations=self.tolerations,
                init_containers=self.init_containers,
                containers=[
                    k8s.V1Container(
                        image=self.image,
                        name="base",
                        command=self.cmds,
                        ports=self.ports,
                        image_pull_policy=self.image_pull_policy,
                        resources=self.k8s_resources,
                        volume_mounts=self.volume_mounts,
                        args=self.arguments,
                        env=self.env_vars,
                        env_from=self.env_from,
                    )