Statistics on table and index usage are updated normally by the downstream master. This is essential for correct function of autovacuum. If there are no local writes on the downstream master and stats have not been reset these two views should show matching results between upstream and downstream:
Since indexes are used to apply changes, the identifying indexes on downstream side may appear more heavily used with workloads that perform UPDATEs and DELETEs than non-identifying indexes are.
The built-in index monitoring views are:
All these views are discussed in the PostgreSQL documentation on the statistics views.