This news kind of slipped by me a few months ago, but in an interview with CVG Remedy finally admitted that they didn't go 360 only because 'sitting on the couch is the most immersive way to play.' I think this confirms that it was Microsoft's decision to not develop it for the PC (not that it was ever in doubt), and it's something that I'm really surprised of considering Remedy's pedigree of being a PC developer (since Rockstar handled their console ports.) I wonder why Microsoft canned it after using it as a tech demo for DX11 several times.
Afterwards, CVG asked Maki to explain why the title was canned on the platform.
"I can't really discuss that," he said. "I will say that it wasn't a technological call. And it wasn't made in Finland."