ConstOrder only — not a grouping. Each feature is its own section headed by its own name, because a region is a feature partition and there is no category above it. A "Regions" heading over these would assert a thing that does not exist, and its empty case would read as "this sheet has no regions" — which cannot be true of any sheet with content.
The formatting half is a set of authored layers, kept apart: direct style
(Fill/Border/NumberFormat/Alignment/Font), conditional formatting and data validation
are separate partitions and are never composed into a per-cell "what won" answer. Composition
is both an expansion — a color scale produces one distinct range per cell — and lossy exactly
where it matters, since a deliberately colored cell and one colored by an inherited band become
indistinguishable.
Reporting order for the feature partitions: where the content is, then what was authored over it.