However, since it is clear that Dwolla transactions are in fact reversible (contrary to their claims)
Did they actually claim this? I've seen them advertise "no chargebacks" as a benefit, but that's still technically true - chargebacks are considerably nastier than merely reversing the transaction. In fact, I'd always got the impression that Dwolla transactions were reversible based on their promotional material.
For the ones that hate all legal terminology, can you explain the difference between a chargeback and reversing a transaction.