If you sealed the unnessesary passages I do not see how the test could not be valid. A hose say right at the rear galley port would simulate the location of the large volume of oil from the pump.
I don't know the details of the test, just the basis of how Atherton
Determine the unequal flow. To me it jives with my dash example.
A long galley opened at the far end, and the large volume of air or oil at the other tends to run right by the nearest passage to the pump until restricted down stream.