Yup, "backyard barbecue" isn't barbecue at all. Southerners will correct people who say this. I am a Southerner, so I will correct people who say this.
Words have meaning for a reason. It's like if you make spaghetti alla carbonara and use bacon instead of guanciale and add cream to it, it's not spaghetti alla carbonara anymore, because you changed the recipe to something else. It's a derivative of carbonara, yes, but it's not "the" recipe.