These aren't real stock, they are "profit participation units" or PPUs; in addition, the fact that there is a NDA and a NDA about the NDA, means no one can warn you before you sign your employment papers about the implications of 'PPUs' and the tender-offer restriction and the future NDA. So it's possible that there's some loophole or simple omission somewhere which enables this, which would never work for regular RSUs or stock options, which no one is allowed to warn you about on pain of their PPUs being clawed back, and which you find out about only when you leave (and who would want to leave a rocketship like OA?).