"Isn't blood plasma 95% water? (by volume) Or are these percentages without the water?"
The percentages presented in my article represent the total volume of what is found in a typical bag of fresh frozen plasma. This of course includes the important constituent of water.
Our body is composed mostly of water. I've read estimates that whole blood is composed of 80 to 95 percent water.
Just like cellular structures (which also have water as a primary constituent) are suspended in the liquid plasma component of blood, so are clotting factors and various proteins and salts suspended in water making the liquid plasma.
When I hear someone say something like "Plasma is mostly just water" it is often said to minimize what plasma is as a biological substance. I'm not suggesting that's the case here. It's just an observation I'm sharing based on experience.