Did you read the whole thing? In that same section of text:

> It is interesting to note that if this were an absolute rule for IT investments (which we believe it is not, as covered in our other sections), then investing in IT would be a waste of resources for the economy as a whole despite benefitting individual firms.

This site is surveying arguments that have been made over the years, one of which is the one you quoted. They're not agreeing with all of those arguments. In fact, they explicitly disagree with the one you're questioning.