I'd rather have it just stick to IPTV. It's the reason I love the Xbox in my bedroom, so I can stream it all through an ethernet cable.
the point is that, people watch TV through cable, satellite, netflix and xbox among other things. the Glass function on the xbox currently is only compatible with watching series and movies through xbox video. Netflix support by letting the glass function hook into the netflix app wouldn't be impossible. But as anyone outside the US knows, a lot of series and movies simply aren't available on streaming services since TV channels in each european country has bought exclusive rights to the shows. netflix can't buy Eruope wide licences.
Now by using the HDMI input. the xbox can hook into your cable/satellite/terrestrial receiver, and by reading the channels EPG on the net, it not only knows what you're watching, it knows roughly where in the episode/movie you are. and you can get all the Glass goodness without streaming. And as the article states, it can apply overlays over the movie, it can give you access to your xbox functions on top. an if the rumors of the xbox running apps, is true, probably Modern UI apps. then you can access all this in top of your movie/series watching.