For more context, Bloomberg also reported on this:
Xbox Executives Were Blown Away by an Upcoming Game. Then They Canceled It.
No paywall version: https://archive.ph/daYYd
But Blackbird’s cancellation was particularly shocking because it had blown away executives at Xbox just a few months ago. During the demonstration in March, Spencer was enjoying the game so much that Matt Booty, the head of Xbox Game Studios, had to pull the controller away so they could keep the meeting going, according to two people who were in the room.
This is a game that even Spencer was enjoying and then they just cancelled it. I have no word.