The water cooling is to assist in transferring heat away from the SoC to prevent thermal throttling. It will not decrease the temperature of the outside of the device, in face I would expect this to increase, if anything.
Completely irrelevant test and so unscientific, it is nauseating. Too many variables. To test this, you need to have identical hardware and software with the exception of the cooling framework. At the very least, you'd have to custom build a note 9 with note 8 internals and a non - carbon fiber matrix. This article illustrated a lack of understanding of heat transfer and complete disregard for thermal dissipation differences in the operation of completely different SoCs.
I am thankful that there are a few people in here that understand that you want the Note 9 to appear warmer as that is the entire point of heat dissipation. The true way to do this test is to track the SOC temp as the test goes. People are so quick to judge...I hope that there will be a more well thought out test in the future.
I wonder how long will it takes to completely dried out the water carbon inside the heatsink. I'm waiting for experts to stress test the phone without the liquid inside. If it performs worse, the same in comparison to Note 8.