When Steve Jobs was around all the really great ideas probably found their way directly to him. If he then decided to call any of those ideas his own and reject the apps, do you think anybody at Apple would defy him?

Whomever that person is now (Jony Ive?) probably got ahold of this app and did the same thing.

Very easy to hide all of this under the veil of 'we were already working on something like that'. The author even acknowledges as much. So blatant theft is basically impossible to prove. But it's pretty naive to think that does not go on.