Not to be contrary - but you missed the point
the electric motor in the test was not fully loaded - it merely was showing that X amount of watts would equal Y amount of thrust
in the tests all th props were basically about the same size and about (reasonably same in blade type - using APC And GWS props)
why dont--you make a thrust stand and try it yourself ?
I was surprised when I did the tests .
efficiency nor rpm was the issue - it done to find how much power was needed to get a static thrust of a given number --equal to the model in question.
using WATTS and an electric motor simply took out the power curves of a IC engine-- which apparantly ,easily confuses the issue.