Re: It would be nice
Privacy matters aside...it should be determined if Apple would have funded his research and development as an internal project and whether they would buy back the IP.
If the answer is no then the point is moot.
You can't stop people pursuing an idea if you've refused to let them explore it via internal channels.
I'm not sure how this looks in a permie contract because I'm a contractor, but in all of my contracts I add a clause regarding any IP that I create. Basically, while I'm contracted they can use any technology that I invent for free but if they wish continue using it after I've gone they need to either license it off me or buy it. The decision is left at my discretion. Usually I don't enforce the clause...I only invoke it if I've been stiffed on payment (extremely rare) or the IP is rolled into a product that is resold to third parties or customers (slightly less rare).
Usually, the result is some sort of lump payment. Not as much as you'd think but enough for me to be happy. I'm not a greedy man...a couple of grand is usually enough.