My understanding is that it's much more common for Europeans to live in or close to cities, or at least walkable neighborhoods, than it is for Americans; and I have this idea that Europeans often will get groceries more often, even daily, since they are often a short walk away. And European dwellings are typically more compact, so there's less storage.
The typical American experience is driving 20 minutes to a superstore (basically a huge warehouse with price tags on every shelf -- an order of magnitude larger than most European supermarkets), stockpiling food for a week or more in walk-in pantries. A month of food is not uncommon here. I think our family goes to Costco and Walmart every 2-3 weeks or so.
So maybe this preparation directive is more relevant to Europeans who typically have smaller dwellings (less storage space) and more fresh food on hand? (I envy it!) Because when I read it, I'm like, "Yeah, most American homes have this already."
Our family also has "go bags" that are ready with about 1 week of portable supplies (food, clothing, light shelter, etc) and a stockpile of food at home, with long shelf lives, in case of any number of events that may disrupt supply chains for months...