Which restaurants were you looking at? There are some that I can think of that might be described as a combination of buffet and table service.
At Captain's Grill and The Wave during breakfast you can either choose the buffet (serve yourself) or order from the a la carte menu.
Akershus at lunch and dinner has a buffet for the first course and then you order your entree from the menu. You serve yourself at the buffet, but your entree and dessert are brought to the table by your server.
Whether buffet or table service, you do not seat yourself. In either case, a castmember will seat you at a table, but at the buffet you will go up and serve yourself while at a Table Service meal a server will take your order after you have been seated and bring your food.
While not a buffet, Be Our Guest is a combination of Quick Service (breakfast and lunch) where you order at the kiosk and seat yourself, but your food is brought to the table by a castmember. Dinner, however, is table service where a castmember seats you and your server takes your order and brings your food.