"Unvested" means just that: The shares have not vested. The shares are not yours yet. You cannot lose something that is not yours. People who get fired before

"Unvested" means just that: The shares have not vested. The shares are not yours yet. You cannot lose something that is not yours. People who get fired before their shares vest, are not "losing" their unvested shares, nor are they "giving back" their unvested shares.