He can (and did) argue that this distinction doesn't really matter, but the distinction is still part of a well-defined standard that The Wirecutter didn't invent.
The point of the article is that the Wirecutter authors don't understand the physics of air filters and gives the difference more emphasis than what actually matters - it doesn't actually make a massive difference in this particular application. For a purifier that intakes and exhausts in the same space, getting more airflow through the filter per hour can mean over time it's basically the same effectiveness, and using a slightly lower spec filter can be a good design trade-off because it doesn't require as much pressure so it can use less power per unit volume of air filtered.
Of course, in other applications, like bringing air into a cleanroom, it makes a massive difference, but that's not what we're talking about.