open-port for sidecar charms: placeholder port remains

When using the (newly supported!) open-port hook tool with a sidecar charm, the placeholder port (65535/tcp) remains configured, as well as the specified port.

I'm invoking the tool here: https://github.com/jnsgruk/zinc-k8s-operator/commit/2076f30311ce915aae7b982de33b03e0b4bb15ce#diff-b9ed39bbc9c0387bd3e07da31d13373745534a1cd723d3e292c73496b12e307cR79

The port is opened correctly, but if you inspect the service with kubectl, you see the following:

❯ k -n zinc get svc
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
modeloperator ClusterIP 10.152.183.142 <none> 17071/TCP 17m
zinc-k8s-endpoints ClusterIP None <none> <none> 2m5s
zinc-k8s ClusterIP 10.152.183.247 <none> 65535/TCP,4080/TCP 2m5s

Note that 65536/TCP is still configured, where only 4080/TCP should be.