I agree, however the royal surveyors worked from a standardized metric given to them, so it’s my contention that a weighted mean of 20.62 +/-.01 inches is the best that can be for a unit measure we’ll never actually be sure of until a contemporary artifact is found (cubit rod). After all it seems irrational for the draftsman/architect would devise a plan to incorporate a margin of error… as you said the variants are or should be assigned to ability/craftsmanship of the ancient surveyors.

B.A.Hokom