While this is a very interesting story in more than one way, and I'm not big on news shaping by editor to tell an overall story rather than give facts, here is how your story doesn't relate to the google feature discussed here: the good news feature doesn't replace the user news, but is specifically requested by the user on each run, by asking specifically for the good news list.

So if someone checked their news on it on that terrible day, they would see both event. If they felt very depressed about it and needed to cheer themselves up, they could ask for a good news of the day; something that they certainly couldn't find on regular news system of the time since the WTC is all they talked about for days.