Of course it's good to walk a lot. Swimming is good too. If general mobility is your goal, that's good.
Despite the article, I've never heard of anybody who lost fat by doing either of those things. Well, maybe if you decide to give a month to hiking the Appalachian trail you will lose fat.
I sort of admire, or envy, people who do not think about their fitness.
How Fit Can You Get From Just Walking? Walking is good for you, obviously. But can it whip you into shape?
Nope. Unless feeble, walks are recreation and not "exercise."