Now it talks about Universal Apps. But it is only Universal "Windows" Apps.
Actually they are called Universal Windows Platform apps. Everybody abbreviates it to universal apps, but at no time has Microsoft pretended to support any non-Windows OS.
The "universal" part is describing device categories. UWP apps will run on any Windows 10 device, including Raspberry Pi and other IoT devices, phones, tablets, business desktops, gaming PCs, Xbox One, Surface Hub, and HoloLens.
(They actually are supporting Linux and Mac with the newest ASP.NET, and even open sourced .NET Core which also runs cross-platform.)