A refined partition is asked for precisely when the relationship between features is the
question — ['formula', 'font'] pairs what each cell computes with the color a human sees, and
a listing that showed only one half answered half of it. Each feature contributes its own
payload and they join in the order the caller named them, so the row reads as the tuple the
partition actually splits on.
Features with nothing to say per region (AutoTable) contribute nothing rather than
an empty column, and a partition where none of them do returns undefined so the listing stays
addresses-only.
One payload describer covering every feature a partition was built from.