It is correct that Cinderella's Royal Table (CRT) is a prepaid dining experience at and the time of booking the payment for the entire meal is due.
If you have a resort reservation with a dining plan already added at the time you book, you will (or you should - sometimes the website doesn't do this correctly) be asked to leave only a credit card hold. (Remember though - the no-show fee is the entire regular price of the meal for CRT - not $10 a person. So you may wish to pay particular attention to the cancellation policy.)
If you want to book CRT before you have a resort reservation with a dining plan, you'll have to pay when you book. But you can then change your method of payment to dining credits. You may be able to do this by calling 407-WDW-DINE. If that doesn't work (apparently not all CMs can do it, or know they can do it) then you can switch payment methods when you arrive at the restaurant and your previous payment will be refunded.