Not sure – I was just following the recipe. But, as a guess, some of it may be flavoring, but most of it is probably that the tannins in the tea help draw out or neutralize some of the “schmutz” for lack of a better term. I have noted a propensity in Korean recipes and in the food dramas to “remove the strong flavors of the meat” for various meats, almost like they want to neutralize the meat flavors and just focus on the sauces and condiments. But that’s all just speculation.