IMO, the main draw to the S8 for a Windows Mobile fan is that this is the device Microsoft is endorsing. You will be able to buy this phone in Microsoft's stores. Otherwise, as Laura said, the apps are available for any Android.
I believe that Microsoft's reasoning behind offering an Android is to offer their customers a mobile solution. With Lumia gone, they do not have a phone. This way they can at least offer their customers something. With DeX and Microsoft's apps, it somewhat resembles what Microsoft tried to create on their own.