If you read further into the booking, you'll see that those 4X bonus miles are for booking with a UA credit card. It's 2X extra miles for any cabin and a further 2X extra miles for a balcony or suite if using their card. Since all those 8X miles are provided by United Cruises (generally, instead of other OBC), I was told that the Shareholder Benefit would still apply. (Unfortunately we canceled the only cruise that I had booked with United Cruises, so I can't be sure of the info being correct).