Two departments are developing it even in a single edition
There is likely two completely different sets developing it right now. You have one doing the touch and one doing the keyboard. You have a different set of people designing the interfaces than the off the shelf icons in the current standard interface. The whole OS is so large that it may look like just 1 little org developing it - but in reality it is likely more like 30 different ones all trying to work together to get it accomplished.