`istio-pilot` does not observe when `istio-pilot` relation is broken

Bug Description

While experimenting with a Charmed Kubeflow 1.9 deployment, I tried removing the relation istio-pilot between istio-pilot and istio-ingressgateway. I noticed that the charm's status stayed active, despite the removal of the relation.

I would expect that the charm observes when that specific relation is broken, which would be under these lines.

I am not sure whether this behavior is expected or not

To Reproduce

Deploy the 1.9/stable Kubeflow bundle and wait until
Remove the specific relation with juju remove-relation istio-pilot:istio-pilot istio-ingressgateway:istio-pilot
None of the charm's status changes

Environment

istio-pilot version: 1.22/stable istio-ingressgateway version : 1.22/stable Kubeflow bundle: 1.9/stable

Relevant Log Output

Additional Context

No response

canonical / istio-operators