I've never made those, but when you make breads/cake/pastry things, you add the water in one go as well. You're supposed to mix the dry and wet ingredients separately and then mix them together. I always figured that as a way to avoid making a mess. (Actually google searching for "Tortilla recipe", some say this, others say "add liquid slowly")

I guess it depends if the person who wrote the recipe is a trained cook or not. So the way you were doing it before maybe was correct for a different type of ingredients, like did you use white or whole-wheat flour? Shortening, butter, or lard, etc.