I noclipped just to see if there was something else, and I found that the blood pool wasn't actually removed, but it is placed just under the floor:
So maybe there is something else that is supposed to raise the blood level so player can land in it?
I also found more secret rooms for the pa07_0011 version, for example in the room with computer panels there is a room hidden in one of the windows with one unopenable door, that is very similar to (spoilers: the door that randomly appears near base in main game):