I was going off from the Disney website. (Granted they aren't noted for being up on their IT)
It says on the CRT page
http://disneyworld.disney.go.com/dining/cinderellas-royal-table/
It's definitely a standard disclaimer, because it mentions alcohol, but I'd definitely have planned on paying a gratuity when I went there.
ETA - Ah ha! I see it!!
Went to pretend to book CRT, and you are charged your gratuity when you make your reservation and pre-pay. It looks like percentage wise it averages out to just a bit more than 15% figured as gratuity.
When I went to check out (for four adults)
Sub Total $179.88
Tax $11.76
Gratuity $27.40
Total $219.04
Total Due Today$219.04
So you will pay for gratuity, and that is paid at the time you make your reservation. When you go to the restaurant, nothing additional is due.
If you are on the Dining Plan, credits will pay for your meal (including gratuity)