By default Pods are not re-created nor the Postgres instances restarts automaticly unless it is required by the high availability mechanism (i.e. when the primary is down or failing). This means that whenever a property that require restarts (special Postgres parameters or Pod configurations) is changed the Pod will require that a restart day 2 operation to be scheduled.
It is possible to configure this rollout strategy in order for a restart of the cluster to happen without requiring to create a restart day 2 operation.
You can configure the rollout strategy of the cluter in the SGCluster CRD updateStartegy section.