AutoScalingConfig 'Invalid stage name' warnings after upgrade

I noticed WARNings like this in some of our logs:

... OverseerAutoScalingTriggerThread ... o.a.s.c.s.c.a.AutoScalingConfig Invalid stage name '.auto_add_replicas.system' in listener config, skipping: {beforeAction=[], afterAction=[], trigger=.auto_add_replicas, stage=[WAITING, STARTED, ABORTED, SUCCEEDED, FAILED, BEFORE_ACTION, AFTER_ACTION], class=org.apache.solr.cloud.autoscaling.SystemLogListener}

After some detective work I think I've tracked this down to 7.1.0 TriggerEventProcessorStage having a WAITING stage and that stage having been removed in 7.2.0 TriggerEventProcessorStage via the SOLR-11320 changes. Haven't tried to reproduce it but my theory is that the listener got auto-created (with the WAITING stage) when the cloud was running pre-7.2.0 code and then after upgrading the warnings start to appear.