I also used an ATM recently in Buenos Aires, and was charged a 13xxx ARS fee on top of withdrawing 60k. I did not see any obvious way of canceling out of this without also aborting the transaction, and a friend reported similar experiences across multiple different bank branded ATMs, so it seems this may be a universal thing in Buenos Aires or Argentina?

The language certainly makes it sound like a DCC situation (extensive FlyerTalk discussion here). However, the transaction details as they appear in the Chase app make it seem like it was actually posted in pesos, and even better, I was pleasantly surprised that Chase reimbursed me the 13k fee (this is a Chase Sapphire Checking account benefit).

Even so, the exchange rate for the 60k was ~1240 (the 13k was also reimbursed at this rate), vs. an XE rate at the time of 1330. So I would still recommend using a credit card where possible and changing at a cambio otherwise.