Of course the restaurants have meat, fish, chicken, and plant dishes on their menus. They are covering all aspects that guests might want. Even if I were to go to an italian restaurant, I'd find a dish that wasnt just pasta. If they were to offer one kind of specialty they would only draw those who enjoy only fish for ex. Give me some examples of what you describe as the same dishes with just different descriptions from multiple Disney restaurants.
Chicken Breast.
BOG - Poulet Rouge Chicken with Faro, Vegetables, and Garlic Sauce
Tutto Italia - Petto di Pollo - Grilled chicken breast, fettuccine pasta, parmesan cream
La Hacendia de San Angel - Pollo al Pastor - Adobo-marinated Chicken Breast with Chili Arbol Glaze and Pineapple Relish and Grilled Vegetables
Brown Derby - Bell & Evans Chicken Breast Red Pepper-Toma Cheese Polenta Cake, Honey-glazed Carrots, Madeira Jus
Big River Grill - Habanero Chicken grilled chicken with sweet and spicy habanero glaze, topped with pico de gallo, avocado and cilantro, served with seasonal vegetables and cilantro lime rice
California Grill - Poulet Rouge Chicken Guava Barbeque, Fried Green Tomatoes, 3 Bean Salad, Black Bean Aioli
Citricos - Chicken Mediterranean creamy Polenta, Tomato Fondue, spring Vegetables, Chicken Jus;
and the list goes on and on. I stopped looking at menus because it was getting tedious.
The recipe is: Grill the chicken breast (maybe you need to throw it in a carboy of marinade first), add the sauce, pull the sides from the steam tray, and serve it up.
There are about a half dozen other chicken dishes that instead of "grill the chicken breast" begin with "bread the chicken breast and deep fry" and then continue with add the sauce and sides.
There is also the oh so creative and different dishes consisting of "grill the chicken breast THEN CUT IT UP, put it IN the sauce, add sides and serve."
There is a place by me that has a dish called "Chicken Ala You" on the menu. Then it lists about 10 ways you can get it - PIcatta, lemon, saltimbocca, etc. At least they are honest about it (and it's a bar, so it is expected, and I think it's about $15 if I recall)
Maybe they should market that to WDW.