True - but he could easily leak the info and if they cant pin it on him then there aint mch they can do. That goes for any NDA agreement. They are breakable. Just saying.
They could sue the pants off of him. So there is a lot they can do. Thats a pretty big gamble to think they couldn't pin it on him considering apple has so much money that launching a large scale investigation would be trivial for them.
Also, who is going to hire someone in the future who shows that level of unprofessionalism and hurting the company over a petty grudge.
People who get to the level he was at get there by playing the game effectively, not by going to the nuclear option immediately.
In short, him disclosing anything would only hurt himself. He would lose a ton of money in a lawsuit and probably in lost future wages and benefits.
To put it in perspective, one time Pepsi was offered the recipe to Coke by a disgruntled employee from Coke. Not only did they not take it, they turned the guy into the police. Had they taken it, they would ahve been liable for a lot of damages, as well as declared that such actions are ok to do (leaving them vulnerable to the same kind of thing from their own employees) You don't play with fire when it comes to corporate espionage and breaking nda's.