Here's the meat: "They're not waiting for the light to come on," Welty said; rather, the human players try to time their buzzer presses so that they're coming in as close as possible to the light. Though Watson's reaction times are faster than a human, Welty noted that Watson has to wait for the light. Dr. Adam Lally, another member of Watson's team, noted that "Ken and Brad are really fast. They have to be."

What a deceptive little statement. If you set the "attempt answer" bit in Watson before the light comes on, and you have the humans attempt to press it as soon as allowable, they will never beat Watson.

Actually, they may beat him a few times per hundred-thousand attempts (assuming Watson gets the "light" and buzzes in via tens-of-microseconds-scale ethernet), but would have to be willing to tolerate what would normally be an unacceptable error rate (if you press early, you can't press again for ~2 seconds if I remember right).