1. Time barring is pretty iron clad. Sucks for the author but consider the alternative where anyone could sue anyone after any period of time.
2. If a court did find in favor of the plaintiff, the court would be more likely to award the 90s cash value of the stock, plus interest, rather than awarding the shares or current market value (damages being how he was actually wronged in the 90s rather than speculating what he might have done with the stock to present)
3. Given 1 and 2, Nvidia is unlikely to make a big settlement, meaning an expensive and risky trial.
Which brings us to hidden reason #4: nobody would pay that much for the rights so it probably isn't worth the author's time. He'd still be the man at the center of the suit: depositions, testimony, cross examination, records subpoenas...