I wonder if maybe there's a difference in usage of the term "sheathing" here. The linked article shows only one layer of sheathing, which is often plywood or OSB but can be an integrated product such as the Zip system. This is how I have understood the term also, back when I did new construction and now that I'm mostly doing repairs. There are multiple layers of different materials in an exterior wall that I wouldn't call sheathing and the linked article doesn't appear to either, but I would not expect to find more than one layer of what in my experiences the industry calls sheathing. I'm not often picky about what word is used though, as long as the meaning is understood.

That said, at least you didn't call it sheeting, like many do.