Supplemental query stats metrics (e.g. the JoinOptimization section) only appear in the recorded query stats entry when the query's initial batch exhausts the cursor. With the default 101-doc batch plus getMores, the entry has no supplementalMetrics at all, even though the query ran join optimization.

Repro: in jstests/noPassthrough/query/joins/query_stats_join_optimization_metrics.js, remove the {{

}} option from any aggregate,  stats[0].metrics.supplementalMetrics becomes undefined. Restore the single large batch and the JoinOptimization section appears.

Expected: join optimization happens once at planning, so its supplemental metrics should be recorded regardless of how the cursor is iterated. Found during review of SERVER-132802.