I don't know how odd that is. Windows 10 Mobile isn't released yet, and Windows 10 has been released. Nobody is going to DEVELOP these on Windows Mobile devices, so it still needs to work on Windows 10 for dev and testing. So developers can start working on using this now, and a later update will add phone support, so they can deploy there as well.
The Candy Crush app is claimed to be a ported iOS app, already available on Windows Phone 8. And I kinda thought the whole Universal Apps thing was architecture-independent.
