Extreme heat & cooling cycles also attracts moisture in brake fluid. I have turned fresh brake fluid to a black color in four days riding in the mountains I also wore out a new set of front brake pads that weekend.
The heat and cooling is at the wrong end of the system!
What I was trying to see is if people, or person, understands what goes on in the system. To answer my own question, the contamination of the brake fluid, once it's in the system, is only at the reservoir end, where it is exposed to air. The reservoir actually "breathes" a little bit as one uses the brake and draw in outside air as the master cylinder pushes a little volume of fluid into the line to push the slave cylinder, and then expel air from the reservoir as the volume of fluid returns into the reservoir. The amount of water that the brake fluid can absorb is a function of time; how much moisture is in the air; and the area of exposure to the air. BMW had done an excellent job with respect to the last item by floating a rubber diaphragm on top of the brake fluid so that the exposure to air is very tiny. The water that is absorbed doesn't propagate to the rest of the fluid instantly by magic, as I suspect that some might think. The heaviest concentration will be in the reservoir, where it doesn't matter at all, but some will migrate into the brake line over time, but it will take a very long time before this contamination gets far. Changing the fluid every 2 years will eliminate the possibility of the contamination reaching even the ABS module completely. Some car drivers claims that DOT 4 fluid should be changed every 3 years, and I suspect that is because, in cars, they have much longer brake lines than what we have on our bike.
The answer to the second part of my question will shed light on your black fluid!
The question is where does the brake fluid degrades? The answer is at the slave cylinder, and only there, where it can be exposed to high temperature. The black fluid is actually carbonized "burnt" fluid!
The final point that I had in mind to lead to is this: why does it matter if the fluid is contaminated with water and have a relatively low boiling point? The answer is that it doesn't . . . . . UNTIL the contaminated fluid reaches the slave cylinder where it can be exposed to the high temperature and boils!
That brings everything back to being on topic with the answer that NO
GS-911 is needed for either throttle body sync OR brake fluid flush. I don't really care what you do with your own bike, but I DO care if misleading information is posted that might lead people into doing things that are unnecessarily (buying a $400 tool that one don't need) or dangerous to either self or machine!