Any water that does enter a brake systems with DOT5 will puddle at the lowest point because it is hydrophobic. That water boil at 212f and cause the pedal to go soft, so care needs to be taken to prevent that. I think the main benefit of DOT 5 is when someone is trying to blow you up (as in combat) because it doesn't burn as easily as glycol based fluids.
Are you sure the fluid you were looking at was not DOT 5.1?
