They didn't make the claim that no namespaces had anything to do with this, that's an inference you're making from the specific list, when it could be for any number of reasons. For example, these are some of the largest package management ecosystems in the world, so they're more likely to be attacked than smaller ones. (You can of course come back and say that there are other massive ecosystems too, but that's kind of my point: there's more to a discussion than a random article listing a few ecosystems.)

I stated my reasoning in my comment: you can typo squat a namespace, just as easily you can any identifier. I don't see any inherent difference between the two.