StatefulSets OutOfSync after enabling server-side apply

[cjyar]

I recently changed my main ApplicationSet's spec.template.spec.syncPolicy.syncOptions to add ServerSideApply=true. After it synced, every Application that contains a StatefulSet is showing OutOfSync. Here's an example of one Application's status.resources:

  - group: apps
    health:
      message: 'partitioned roll out complete: 1 new pods have been updated...'
      status: Healthy
    kind: StatefulSet
    name: postgres
    namespace: postgres
    status: OutOfSync
    version: v1

The StatefulSet itself thinks it's healthy. And before I changed ServerSideApply, ArgoCD thought it was healthy and in-sync also. Now suddenly it thinks it's not. I've tried some tricks like force syncing, but it doesn't change the behavior.

Also, argocd app diff shows no diff. (I'm using argocd core, so I only have CLI access to view diffs.)

Here's the status of the StatefulSet above:

status:
  availableReplicas: 1
  collisionCount: 0
  currentReplicas: 1
  currentRevision: postgres-7b9796d844
  observedGeneration: 39
  readyReplicas: 1
  replicas: 1
  updateRevision: postgres-7b9796d844
  updatedReplicas: 1

Any idea what's going on here? How does ServerSideApply change ArgoCD's understanding of whether the StatefulSet is synced?