I'd guess he expected a 99% failure rate in exchange for a few highly polished gems that might be featured in a MacWorld keynote, or at the very least make it into a shipping product he could show off to his family and or friends.
I think anyone should be allowed to feel disappointed at a 100% failure rate over three years, no matter how many NDAs they signed.
He was working in highly conceptual R&D, he could have worked there for decades and never had anything reach the public in any recognisable form, let alone make a MacWorld keynote.
If you want public recognition it's not a great area to work in regardless of the company.
If he made a mistake surely it reflects on him rather than Apple?
If you don't like the terms, don't sign the contract. If he's good enough to get a job at Apple I suspect it wasn't his only option.