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
in_cluster: Optional[bool] = None,
        cluster_context: Optional[str] = None,
        labels: Optional[Dict] = None,
        reattach_on_restart: bool = True,
        startup_timeout_seconds: int = 120,
        get_logs: bool = True,
        image_pull_policy: str = 'IfNotPresent',
        annotations: Optional[Dict] = None,
        resources: Optional[k8s.V1ResourceRequirements] = None,
        affinity: Optional[k8s.V1Affinity] = None,
        config_file: Optional[str] = None,
        node_selectors: Optional[dict] = None,
        node_selector: Optional[dict] = None,
        image_pull_secrets: Optional[List[k8s.V1LocalObjectReference]] = None,
        service_account_name: str = 'default',
        is_delete_operator_pod: bool = False,
        hostnetwork: bool = False,
        tolerations: Optional[List[k8s.V1Toleration]] = None,
        security_context: Optional[Dict] = None,
        dnspolicy: Optional[str] = None,
        schedulername: Optional[str] = None,
        full_pod_spec: Optional[k8s.V1Pod] = None,
        init_containers: Optional[List[k8s.V1Container]] = None,
        log_events_on_failure: bool = False,
        do_xcom_push: bool = False,
        pod_template_file: Optional[str] = None,
        priority_class_name: Optional[str] = None,
        pod_runtime_info_envs: List[PodRuntimeInfoEnv] = None,
        termination_grace_period: Optional[int] = None,
        configmaps: Optional[str] = None,