We know it was rushed, and we know why. Scott Forstall (the architect of iOS 1-6) was fired, and Jonathan Ive promoted to VP of Design, on 29th October 2012, 11

We know it was rushed, and we know why. Scott Forstall (the architect of iOS 1-6) was fired, and Jonathan Ive promoted to VP of Design, on 29th October 2012, 11 months ago. 11 months -- really 7 months, as it had to be mostly done in time for the WWDC demo -- is an astonishingly short length of time to do a ground-up UX redesign of an OS. The only way it's possible is to parallelise the design process to some extent, which makes consistency issues inevitable.