A region is uniform by construction, so the anchor cell's read describes every cell in it —
that is what makes a payload one line rather than a column of repeats. It is also why the
formula payload is honest for a block: getRegions groups formulas by canonical R1C1, so
D2:D4 really is one authored =B2*C2.
A payload is never a computed value. =B2*C2 is authored content, the same kind of fact
as a fill color; 2398.8 is data, and data is a values read. This is the line that keeps the
sheet report bounded.
A feature with no describer here prints its address alone, which for most of them is a lie of omission rather than a fact — see the TODOs below. The goal is that every partition says something useful about what it found.
The payload describer for one feature, or
undefinedwhen the address is the whole fact.