See: https://cockroachlabs.atlassian.net/wiki/spaces/CDC/pages/2398552506/22.1+Metrics+Labels+Acceptance+Testing for reproducibility

When creating a changefeed using the CREATE CHANGEFED ... WITH metrics_label=X configuration the user must set the cluster setting server.child_metrics.enabled=true in order for the feature to work. If they do not set this cluster setting, we still allow them to create the changefeed, but the metrics label feature is silently not applied. We should instead fail the changefeed creation when this happens, with a similar error message to when COCKROACH_EXPERIMENTAL_ENABLE_PER_CHANGEFEED_METRICS=true is not set:

Jira issue: CRDB-12779

Epic CRDB-13931