Ok makes sense now and looks sensible. Here's W estimates from flow rate and delta t across waterblock (adjusted 0.02C to account for difference in probe without PC running):
Block used in today's testing is the Swiftech MCW5000-A; deltaT CPU-wb in looks like this:
If you take the average watts from top graph (73.14W) then you can estimate a C/W:
All becomes clear now (and more test data as f(MHz and VCore shall be collected over the weekend)