A layout optimization that changes user perception of the report but not the semantic rule being tested

Hierarchies are automatically created by Power BI, although plausible for report design, it describes chart presentation choices and not the specific feature semantics asked here.

In Model view, right-click a field and Create Hierarchy, then drag other fields into it

Hierarchies can only be created in Power Query, although plausible for report design, it describes chart presentation choices and not the specific feature semantics asked here.

Use DAX to create a hierarchy measure, however, this interpretation reflects visual formatting behavior rather than the analytical intent evaluated by the question.