>it is reasonable to assume that the point here is that a full-screen

wrong. you answered under the context of yunwal's comment https://news.ycombinator.com/item?id=49630931#49634166

  > None of that matters for a phone.
  Of course it does. They show the most basic example right 
  on the page, which is that you can side-by-side full screen 
  apps. 

which is talking about the case of two separate apps running side-by-side (unfolded), as was shown in one of the pictures of the device.