Your point is based on the false premise that literally no one is supposed to know his identity. In reality, the claim is not that literally no one knows his id

Your point is based on the false premise that literally no one is supposed to know his identity. In reality, the claim is not that literally no one knows his identity, but rather that his identity has not been publicly confirmed. Most likely there are quite a few people who know his identity, like his art agents, financial and legal representation, friends, etc.