Depends what they mean by Productivity. Other things can be productive other than Labour. Also it still doesn't mean you should be paid twice as much.
If I can hire 3 unskilled workers for less than the price of a skilled worker that is twice as productive as a single unskilled worker. I would just hire 3 unskilled people.
If I can hire 3 unskilled workers for less than the price of a skilled worker that is twice as productive as a single unskilled worker. I would just hire 3 unskilled people.