Re: No, it's not
While I do agree with your first two points (can't run W32 native code and touch interface compromise) you have missed one important element, that the author also either didn't know or didn't mention. Particularly when they mentioned it not accepting prior WinPhone8.1 apps.
Something important and new in UWP apps, as opposed to the previous Win8/WMobile8 apps is a layer of interface tools. These were specifically implimented to allow interfaces to change depending on what they were seen on (xbox, IoT, desktop, mobile, tablet). In fact, the app doesn't even need to close to change it's skin. It happens in real time while the app is still running.
If an app made for Windows Phone 8.1 was allowed on Continuum, it wouldn't know what to do and just mirror directly onto the screen, either giving a tiny, phone shaped window on screen akin to an emulator (which would be near useless as it would combine the worst bits of both in clumbsy big finger buttons and tiny real-estate, rather than the best of both) or simply streeeeeaaatch out the window to full monitor size, which the author DOES mention and how ordinary that approach can be.
These tools mean you can actively adjust the layout of your app, so on the phone it has the phone interface (which is ideal for that form factor) but when it gets goes to Continuum mode, it can do anything from minor adjustments to complete overhaul. All this without changing the coded logic of the app itself.
So, provided the developer bothers to do so; the Continuum interface can, like Excel does, completely change it's appearance to reflect the current device's capabilities. Meaning you could have W32 era size buttons and text, etc all intended for mouse and keyboard entry when those things are available.
Biting the hand that feeds IT
