There appears to be no consensus within the Windows community on the criteria an app must satisfy to qualify as a UWP app. That's even though Microsoft's definition should make this a non-debate:
All appx packaged applications are UWP :)— Matthijs Hoekstra (@mahoekst) August 7, 2017
i.e. anything on the Store.
Apps that target the UWP can call not only the WinRT APIs that are common to all devices, but also APIs (including Win32 and .NET APIs) that are specific to the class of device that the app is running on.
In other words, the Spotify apps on the Store (PC via Centennial and Xbox via Westminster) are technically UWP apps like Appy Text despite their Win32/web roots. Although this technicality is generally acknowledged, the usual counter-point is that apps like Spotify's are not true UWP apps because they don't leverage the UWP platform's built-in features and universal building blocks to create a UX that works well with a variety of devices, screens, and input methods. In many ways, none of this really matters seeing as the majority of Windows users won't have any idea what UWP even is. But what this difference of opinion indicates is a need for Microsoft to acknowledge that there are different flavours of UWP apps through official naming conventions. This doesn't necessarily need to be communicated to users, but it will help move the UWP conversation forward by adding necessary nuance to positively steer the conversation towards more meaningful discussion related to the UWP mission. For example, shifting the debate from a dismissal vs defence of Spotify's UWP credentials to identifying steps needed so that UWP web apps offer a more native-like experience. Or for UWP Win32 apps' UIs to feel more modern.Wednesday, August 9 - 12:36 pm