I have often seen pedestrian signals where the countdown ends when the red light turns on (so the countdown is still going during the yellow). My reading of the article was thus that the rear-enders are choosing to run more yellow lights, not that the rear-ended are choosing to stop when it's still green. In that case, it's the rear-enders who are paying attention to pedestrian signals and changing their driving as a result, and they're hitting people who are stopping as they approach a yellow in the normal manner.