If I got a cup of milk and sprinkled tealeaves on it and added a pinch of hot water to it, would it be a cup of tea or a cup of milk with some **** in it? I mean, it has the exact same ingredients as a cup of tea, so it must be a cup of tea, right?
No.
A Chicago deep dish pizza is a pizza because it is called a pizza. The concrete ingredients of something doesn't determine what it is named. We have linguistic concepts, how they are tracked isn't determined by their correspondence to real concrete material in the world. We don't call human lungs bodies of water because they are 83% water.
John Stewart might not literally have a part of the male reproductive anatomy where his head should be, but it is still perfectly understandable and correct for me to call him a dickhead.