At the 1:13 mark we can see the SkyDrive app, sporting a large black bar which is not present in the current Windows Phone 7 app.
If the video depicts a real app, it would likely be how Windows Phone 8 will handle the difference between aspect ratios between HD and so-called HD+ screens and current WVGA screens.
With the HTC 8X having a 1280×720 screen, which is 16:9 aspect ratio, vs the 1280×768 screen for the Nokia Lumia 920, which is the same 5:3 aspect ratio as WVGA (800×480), it could mean 80 pixels are regularly wasted on the HTC 8X to allow older, unoptimized apps to scale without distortion.
The solution is reminiscent of that of the iPhone 5, which takes older iPhone apps and centre them on the screen.
We will not be able to confirm this properly until Microsoft releases the Windows Phone 8 SDK, but it could be one more reason to buy a Nokia Lumia 920 over a HTC 8X.