Uhhh... not to throw mud on your cake, but Apple has been following a trend with iOS for a while now and tend to merge more and more of it into OSX, hence these developments. When Apple was still lingering in a skeuomorphic pseudo-3D la-la-land, the world made a few turns and turned out to be flat after all. Whether it was Google following Microsoft or the other way around, both presented a 'fresh new look' which was mostly marked by flatness and abstraction. Apple followed suit in iOS7/8 and now in OSX 10.10.
I'm talking about the relationship between Apple and devs making apps for their platforms. Not about "who invented flat first" (answer: the 70s did, but that's another story).
Picking "who dun it first" arguments online is so old, dude. So old.
