[Metrics][Discover] Fix multi-dimension breakdown picker to match current grid

src/platform/packages/shared/kbn-unified-chart-section-viewer/src/components/observability/metrics/hooks/use_fetch_metrics_data.ts

@@ -21,8 +21,8 @@ import { getEsqlQuery } from '../utils/get_esql_query';
 
 /**
  * Fetches METRICS_INFO when in Metrics Experience (non-transformational ES|QL, chart visible).
- * When selectedDimensionNames has more than one item, refetches with a WHERE filter so only
- * metrics that have at least one of those dimensions are returned.
+ * When selectedDimensionNames is non-empty, refetches with a WHERE filter so only
+ * metrics that have all of the selected dimensions are returned.
  * Returns loading state, error, and parsed metrics info for the grid.
  */
 export function useFetchMetricsData({

src/platform/packages/shared/kbn-unified-chart-section-viewer/src/components/observability/metrics/metrics_experience_grid.tsx

@@ -103,6 +103,7 @@ export const MetricsExperienceGrid = ({
 
   const { toggleActions, leftSideActions, rightSideActions } = useToolbarActions({
     allDimensions,
+    metricItems,
     renderToggleActions,
     onDimensionsChange: onToolbarDimensionsChange,
     isLoading: isDiscoverLoading,