"Universal app" is a nice term though, isn't it? It speaks to the idea of a single app that can run everywhere. We know that's not the reality but it seems like what a lot of people want to aspire to.
iOS already has "universal apps". These are a single packaged application that can be deployed to both iPhone and iPad and the app will adjust its UI (and behaviour) as appropriate to provide an optimised experience on both types of device. Anecdotally I've heard from people within Microsoft who speak to developers, who develop for platforms other than Windows, who are amazed that despite all this talk of "One Microsoft" and a common design language across all platforms it is still necessary to build separate apps for each platform.
Maybe talking about something with the same name as a type of application on iOS will make some people think that "universal apps" on Windows work just the same...
So, what of these templates if they're not apps?
"Universal apps", in the Windows sense, are a solution that contains 3 projects: One is the Windows apps; one is the Windows Phone app; and one is a new, special kind of shared project that contains files and resources that are auto-magically included in the other 2 projects when they are built.
In Microsoft's defence, they have done a lot of work to be able to use the same UI and code files in the projects for both type of app.
What about using the "same" app on "big Windows" and on the phone?
So, in conclusion:
- The term "universal app" is confusing and means something different to what it does on iOS.
- "Universal apps" on Windows are a way of reusing code and assets to easily build versions of an app for both Windows and Windows Phone.