I can be a whole lot of help, since I had it over a year ago, but I'll try. It was delicious! I remember eating the whole thing, and I hardly ever clean my plate. I don't remember specifics, but I do know it was good enough that I plan on having it again this year when we go.
It's been a while since I worked for Disney but I can tell you at that time Frozen grouper or snapper would never have been used. Grouper is a fish that can be had fresh year round. Part of the year it might be Florida or gulf grouper and the rest of the season it may come from elsewhere but I would be very suprised it is a previously frozen fish.