It's one thing to port a specific application and work out all of the kinks. It's another thing entirely to claim that millions of different applications will be able to make the transition. Even the article points this out: Winulator isn't compatible with Starcraft: Brood War yet. It's a work in progress (each game requires specialized tweaking in order to work).

Microsoft is not willing to tweak every single application to make sure it works on Windows RT, and neither are the developers of most of those programs.