Atari is now just a trademark that gets sold left and right. I don't know why this is happening but no one from the 80s is making this call. Those people went from cradle to grave engaging in anti-worker action and giving into the worst and most perverse incentives capitalism has to offer. They retired wealthy and all of this awfulness paid off. This is why modern video companies are run similarly. As a dev or artist, you're not getting ownership either. You're work for hire and will be treated as such.
The division asking for this author is Atari XP, which sells rare and unreleased games, which is most likely looking for this author because this might have a copyright claim. The profit incentive drives this question, not any sort of altruism. Atari XP doesn't know the contract signed by this person and Atari and if they try to release this game commercially they could be sued if they infringe on his rights. If there's no contract at all, then this author would probably have the full life of copyright on their side.
If this person is found and also found to not have a claim, then this game will be released with the creator getting nothing that isn't specified in the contract. This is not done for the love of old video games, but to create and maximize profit. Doing things like this is how the leadership of Atari XP got there and maintain their position there and how they will advance their careers past it.
The author remaining anonymous stops Atari XP from monetizing this old work and might be intentional to keep this game from being published. If published it will enrich some company they havent had a relationship with in decades and most likely don't care for (Atari ex employees seem very bitter about their time there).
Or considering this person has never spoken up all this time all this time, perhaps they passed away long ago, well before most of HN was even born. The hypothesized copyright would move to their heirs, who may be entirely unaware they own this game.