The article quotes a former SW pilot who said the policy had to do with on time performance. That is braking at speeds over eithty knots required a longer time period to allow for brake cooling.
That is what brake fade is all about...heat. Over heating the brake friction surfaces reduces braking power. The heat quickly soaks to the hydraulic fluid, reducing such even more.
Haul your vehicle down quickly from 100 mph, then drive off and try to stop in a normal manner...your brake pedal (non ABS) may go soft and the vehicle will not stop as expected. For ABS, you may still have pedal but less stopping power.