I am sorry you do not accept a medical fact as fact. A vegetative state is not a theoretical construct.
From your description of the 'fact', it seems to me that noone is capable of determining whether facial expressions, smiles, trying to get out of the chair etc are mere reflexes. So when a medical professional asserts such a fact, I am suspicious that they have repeated it to family members so often when they pull the tubes that they have gradually come to believe it is true with no real basis to believe it one way or the other.