Don't worry about it too much. That article doesn't link to an actual study, so we don't know what it says. The article itself doesn't mention if the study tried to distinguish between correlation and causation with fast walking and longevity.

For an example of the problem, I tend to walk fast. But also, my family history shows a very strong tendency toward longevity (most of my known ancestors who didn't die as a result of injury lived to be more than 100 years old). If I live that long, is it because I walk fast, or because I have favorable genetics? This study doesn't appear to be able to distinguish between the two.

So, this is a single article vaguely discussing some findings of some sort that were made by a pedometer company for marketing purposes. I would take anything it says with a huge block of salt.