In the keynote they seemed to imply that existing apps would appear sharp on the new displays, and this sort of rendering trick would achieve that.
I think the apps will look sharp because of a good scaler, not because it's messing with the UI View hierarchy.
I get the sense the author of the article isn't aware you need new launch images to make the app iPhone 6/6+ 'native' ?
I don't think it quite works that way. In the past, your iPhone app was designed to run on iPhone only and it upscaled if you attempt to run it on iPad and the OS knew it had to do this due to a checkbox setting in xCode.
Nowadays, most apps are universal and runs on any device by adjust the output according to device resolution and given scale factor. Basically the scaling is handle internally by the program and not by the OS as described above. In theory, your app should be future proof if you did this correctly.
That said, you need HD Retina graphics so that your code avoids upscaling images. Beyond that, everything else such as fonts are not upscaled but drawn to scale.
http://oleb.net/blog/2014/08/replacing-launch-images-with-st...
I'd imagine the scaled up apps will also look slightly blurry, but how much is to be seen once we get the devices.
A developer has to build the app under iOS 8 SDK with new launch images for the iPhone 6 and 6+ to use the native resolutions of those devices.
The frames will then be 375x667 and 414x736 for the iPhone 6 and iPhone 6+ respectively.
So the auto scaling is a stop gap, you really need to have the app running at the native resolutions to look as best they can.