Today QueryStats is on by default on 6.0+ clusters on Atlas, which is virtually every user cluster on Atlas. Our current evergreen tests (correctness and perf) do not enable QueryStats by default and rely on the QueryStats passthrough suite for coverage. We should flip the defaults to always running QueryStats to match the real life behavior on Altas. We can rework the QueryStats passthrough to test the "QueryStats off" behavior instead.

Note that EA and community still runs with QueryStats off by default. So having a good coverage with QueryStats off is also important.