The GPU passthrough is relevant because it means that you don't need to build out a whole machine for just windows to isolate it. Instead you put a GPU in either your server (or your main machine) pass it through to a windows VM and then stream from it (through something like steam big picture, nvdia streaming, sunlight/moonlight, etc) knowing that the only info Microsoft slurps up is gaming related. You can even isolate windows from the internet if your gaming habits don't require it.