Yes, that's an argument a lawyer might make, but I disagree with the premise: Any reasonable interpretation of "agreeing to purchase" takes into account the entire dialogue between the merchant and customer, in which case the merchant told the customer two different things, and the customer reasonably didn't notice that one was different. There's no reason to assume about which version the customer agreed to.
Can't wait for airlines to add another confirmation screen to the checkout process. Please type "Yes I want this flight and I double checked the dates are correct" to proceed.
