Jenkins X pod templates not upgraded when running jx platform upgrade

I'm trying to add a custom pod template "maven-java11-nuxeo" to the platform team's Jenkins X instance.

I've defined a myvalues.yaml file in ~/.jx and I'm running

jx upgrade platform --local-cloud-environment --namespace=platform --always-upgrade --batch-mode

As a result, I don't see any change in the Jenkins X UI: Manage Jenkins > Configure System > Kubernetes > Images. My custom pod template just doesn't appear.

Yet, I've noticed that the config map is there:

kubectl get cm jenkins-x-pod-template-maven-java11-nuxeo -o yaml

I had restarted Jenkins manually between some tries but this didn't help.

Also, at some point, but difficult to say when, maybe one day after the first try, the new pod template had appeared in the UI. I've deleted it so that the issue can be replayed.