See, the problem is, dishonesty and mistaken identities can run both ways--I can easily imagine offering to switch the unproven snake for a different 100% het, only to have some completely different snake returned to me in the exchange.
I'd only offer to switch the snake for a different het of equal value if I the person trying to return it sent me pictures of the unproven het and the pictures matched those of the snake I'd sent. But that would require me as the breeder to take pictures of all my hets before sending them out...