My guess is these employees weren’t chosen randomly. If they refuse to coöperate with Apple, they’ll get personally sued as well.
And the reality of the matter is, given Altman’s public persona and reputation, there is a good chance an AG somewhere starts looking at whether these folks broke any laws.
But it doesn't follow at all that Apple is threatening to sue them. A long time ago, in an unrelated case, I got a letter like this because I was in the room when a certain decision was made and happened to have some notes about that meeting. But there was no chance I would be sued. I wasn't the decider, and was basically a third-party involved.
This isn't law and order and that's not how civil litigation works.
Might have to make some phone calls to my local representatives now...