FWIW, if you look at a hypothetical example of 2 gpm and a pressure drop through the block of 25 inches of water (7.6 lpm, 6221 Pa), the related power is only ~0.78 watts. That may be representative of a fairly high-flow, low-restriction block. Doubling the delta-P doubles the energy to ~1.6 watts. In this general range, all the blocks on the graph fall within 0.02 °C/W (or about 1.2°C for a 60 watt load).
Better to merely forget such minor details and simply buy the only block that really stands out from the rest, and it
isn't on the above graphs.