Win2D for UWP, and DirectX for .NET Framework

Hello,

Thank you for the comprehensive cross-platform 2D Graphics library...

What was a driving motivation for not selecting Win2D as the API for UWP Platform?  As Win2D is native to UWP. Win2D API is very similar to API of SharpDX.

Also, SharpDX (DirectX) could be used for ".NET" (Full .NET Framework), instead of "System.Drawing".