He doesn't have to prove this affected him negatively to win the suit. He only has to prove Apple knowingly disclosed false or misleading information. See my previous comment.
He's not suing Apple. He's suing the people who worked there. So disclosure, if it comes in at all, is shaky grounds.
And while technically he might get a "win" just to show bad behavior, he's suing under the tort system which exists for redressing damage done to people and trying to make them whole again. At most, he might argue if he'd known he would have sold all his stock - and lost out on the run-up so by keeping him in the dark and in the stock the shareholder prospered. Or he can try to make the case that the stock price will drop because of the eventual settlement - hardly.
So if the system really worked like it's supposed to do, determine when people have been hurt and make them whole, this guy would be laughed out of court (hopefully early enough that Tim Cook, the Jobs family, and the other executives aren't drained by legal fees - that in our legal system they won't be made whole if they are found to be innocent). But the system doesn't work like that, they could get a big award just because "bad stuff happened" and a settlement is likely just to avoid the legal fees and the possibility of a big award regardless of the lack of harm suffered by the person.