I'm pretty sure this guy has no idea what he's talking about. Every airport in the US in a city with a subway (or equivalent) has a station at the airport. Off the top of my head ATL, ORD, JFK, SLC, OAK all do.
And the point of the plane trains is to move people between different terminals. I have less international airport experience but the only way they don't have them is if they use buses instead.