You are the one who is largely incorrect. Compare Royal Dutch Shell Class A (Dutch) shares, which have 15% Netherlands tax withheld on dividends, and RDS Class B (U.K.) shares, which have no U.K. tax withheld, or any other U.K. company which has no U.K. tax withheld from the dividends.
Also, 15% Netherlands tax will indeed be withheld from dividends paid on shares held in a retirement account. A large number of internet sources can confirm this.
1) The U.K. does not have a foreign dividend withholding tax.
2) The 15% Netherlands withholding tax will be withheld whether or not the shares are held in a retirement account, and for a retirement account you cannot claim a foreign tax credit.
From the S-4: "The receipt of New CF ordinary shares in exchange for CF Holdings common stock pursuant to the combination will be a taxable transaction for U.S. federal income tax purposes. A U.S. holder of CF Holdings common stock will generally recognize taxable gain or loss equal to the difference between (1) the holder's adjusted tax basis in the CF Holdings common stock surrendered in the exchange and (2) the fair market value of the New CF ordinary shares received as consideration in the combination. "
Additionally, 15% Netherlands tax will be withheld from future dividend payments.