Testing after washing is absolutely appropriate.
Using someone else’s data to compare to yours to see how well you did is also on point.
…but; you want to know how YOU did, so it YOUR results that are most relevant, not some other guys.
You can also get at the problem by knowing input potency and output potency.
Calculate total cannabinoids in vs out. Compare to total cannabinoids in “waste”.
Should balance. (See: How many lbs of biomass is it taking you guys to produce 1 kg CBD distillate? - #28 by cyclopath)