I think you may be right but also may be wrong. If that was indeed the case, they wouldn't have to respond to him for a whole year. nVidia knew they screwed up back in 1996, but was 100% uncertain like you are. There is 5-10% chance that a judge would accept this on the basis that this was grossly incompetently misrepresented in 1996 and OP actually has some ground for suing. There is serious financial loss here. If I received 1000 shares from Meta for my work during my full time employee and then keep thinking I had 1000 shares invested for 30 years, but turns out no I do not, that's a big loss!
It’s the other way round. For 30 years he has happily believed that he received 16k shares. Now he learns that he was owed another 7k at the time but neither party in the transaction noticed and he wants them to pay the difference now.