[Question] GrafanaNotificationPolicy for externally-managed data sources

[npapapietro]

I have externally managed alerts configured through the prometheus operator that has alerts configured through PrometheusRule. With this I have configured a Notification policy

apiVersion: grafana.integreatly.org/v1beta1
kind: GrafanaNotificationPolicy
metadata:
  name: notificationpolicy-sample
spec:
  instanceSelector:
    matchLabels:
      dashboards: "grafana"
  allowCrossNamespaceImport: true
  route:
    receiver: slack-alerts
    group_wait: 10s
    group_interval: 1h
    repeat_interval: 3h 
    routes:
      - receiver: slack-alerts
        object_matchers:
          - - external_label
            - =
            - my_instance

I can confirm in the Alert Rules view in grafana that there are firing alerts with the label external_label=my_instance but doesn't not get propagated to notification policies.

I have manageAlerts: true as well for the prometheus data source

Am I misunderstanding how to configure alerts with grafana operator?