In dist/stat_data.py we define several statistics that are both connection and data source statistics. However none of the data source statistics are ever set.
There are several commented out lines in test_tiered04.py for data source statistics. Once the statistics are set those line should be turned on.
Also, it seems like the tiered_work_units_created and tiered_work_units_dequeued are in the wrong place. They're defined in the connection and data source area, but really seem to belong in connection-only, up where flush_tier is defined.