You can’t form a differential diagnosis without a complete history and physical exam, labs and radiology. You certainly cannot make a diagnosis by exclusion without getting all the facts necessary to exclude everything else. That’s a basic lesson since you brought up this analogy. The truth is we don’t have all the facts we need to make that determination. Therefore you have not excluded every diagnosis. You have simply fallen trap to a very common form of bias. You (we) are long and this diagnosis fits your interests best.