Restarting the catalog destroys in memory catalog objects (Database, Collection, IndexCatalog[Entry]) and reconstructs them based on the state of the storage engine. However, because the catalog is not versioned, this process loses versioning information, in particular the "minimum visible snapshot" value. That value is used to prevent reading the catalog at too early of a time.
Typically with rollback, those values are get filled in to correct values when replication recovery plays forward from the stable timestamp. However the restart catalog command does not roll back data, and therefore does not perform any replication recovery.
This case is only problematic in testing, as the restartCatalog command is test-only.