Without taking any blame off Microsoft, I'd like to argue that while you boast of so many years of embedded development and understanding that GPUs don't do anything without drivers; when you make your argument it still comes off like you don't understand that.
Microsoft CANNOT develop drivers of any respectable GPUs without enormous help from Nvidia or AMD. And they don't even try, in any significant way, other than supporting graphics companies. They could have tested and released lists of supported GPUs if the list were small, like Apple's. It's not so they can't, not without 200 times as much effort as Apple which they are unwilling to invest. Probably they should, but you can't pretend they don't have orders of magnitude more work to do in this area than Apple, precisely because of hardware variety. That much is just for graphics.