Apparently it's still in the developer agreement you have to sign in order to be allowed onto the App Store [1]. Apple can't really blame people for spreading misinformation if the only reason this isn't true is that they usually decide not to enforce the clause.
> In the event that Apple receives any notice or claim from a payment provider [...] Apple will have the right to retain its commission on the sale of that Licensed Application, notwithstanding the refund of the price to the End-User.
"From a payment provider" means a chargeback, e.g. a customer calls their credit card company the charge was fraudulent, and the credit card company files a dispute code against payment provider (usually Visa 83/JCB 546/Mastercard 4853/Mastercard 4863 depending on the case). In this case it's not uncommon to not refund the fee. In fact, many payment providers will also charge you extra fee for the dispute (e.g. Stripe charges $15[1]).
There's also filing fee in case the merchant trying to fight the dispute and lose. The fee varies by network: $500 for Visa, at least $600 for Mastercard.
> In the event that Apple refunds any such price to an End-User, You shall reimburse, or grant Apple a credit for, an amount equal to the price for that Licensed Application.
And the sentence above that covers the regular refund too. Not sure why you left this part out of your quote unless it is your point that at least the practice in case of chargebacks is fair (to which I agree).
I'm not a lawyer (e.g. I don't know how far "In such cases" clause applies in the statement), and simply want to provide a justification for the clause I'm personally familiar with (a chargeback)
1: https://news.ycombinator.com/item?id=23992510