This is true, not denying that. But what I am denying is that law is rational and has a sensical internal logic that can be exploited. If the state decides that the law is going to enforce some contracts which have no exchange of value, they will. If they decide they want to not enforce other contracts which have no exchange of value, they won't.
Law isn't some platonic entity that is static, it is essentially whatever the state decides it feels like enforcing at any given point. And you are going to do it because if you don't they will kidnap you and rob you of your possessions. So it doesn't matter if you think you found some sov-citizen workaround in a contract, if the state doesn't feel like siding with you it won't. Laws aren't real.