If you're part of the OHA you're not allowed to release a device running a forked version of Android. So that means Samsung can sell Android, Windows or Tizen phones.
Now it appears Google doesn't even want to share the same device with another OS.
It makes sense. Nothing will show a user how utterly $hitty Android is then to run it on the same device as Windows and let the user experience the glaring shortcomings first hand.
And people wonder why Apple says they won't...