There is no duress here; they reached out to him about how getting him to waive his claims. He had no obligation to do so. Likewise, they had no obligation to accept his offer and could have simply decided to risk it.

IOW, there's a snowball's chance in Saudi Arabia that these guys will be able to recover any money they pay to the "lawyer" to settle his "claims" against them.

The lesson to take away: have an employment agreement with everyone you bring in to work for you, even if it's just a simple one page document.