They did, however, create a set of design principles for user interfaces for computer applications (inspired in large part by particular pre-computing graphic design styles, but also including particular principles for providing affordances and feedback for interactive applications within that graphic style.)
Yeah, and iOS isn't following most of them. http://msdn.microsoft.com/en-US/library/windowsphone/design/... I didn't look at every single one, but having used Windows Phone 7&8 for over a year, and scrutinized the released slides from iOS 7, I don't see any place where they are especially similar.
I didn't mean to suggest that it was, I was trying to suggest a better focus for discussions of whether iOS design was following Microsoft in any substantial way than either "flat rectangles", or even "what bits seem generally similar to Win 8".