I think the point is adding extra restriction on top of the CPU and GPU Block. Not sure it matters that much in real world operation.
Maybe this will quench your thirst for knowledgehttp://www.xtremerigs.net/2013/08/09/how-to-read-a-pressureflowrestriction-plot/

works fine. Got my flow meter set up last night and i am getting 2.9L per minute at half speed on the 5. So in my case every minute the entire coolant content ahs been round my loop once.Allows me to see how the heat builds up and cools down round the loop.
I'm curious, do you notice much temperature difference from the different probes?
I would have though with the level of flow you have that the temperature would equalize.