As a guess: the first pic has translucent floor blood (presumably a flat model) whereas the second has opaque. To continue guessing, I'd suggest that the translucent blood in 2.0.04 is in fact correct and the opaque blood in 1.8.09 is a bug.
The pictures don't do justice apparently. 2.x makes the blood more translucent than previous versions. Whether that is intended or not is up in the air.