2-2-2, 3-2-3, 2-2 lines, ect. means the number of Basic, Stage 1, and Stage 2 Pokemon, right? How can a player use three Stage 2s if there are only two Stage 1 Pokemon?
Your assumption is correct, and it is attainable through Rare Candy. A lot of times the middle stage is played one less than the others because of Rare Candy, and consistency's sake.