Argentina Pesos credit card exchange rate

We just entered Argentina and will be here for a month and we made two purchases on a credit card (that doesn't have foreign exchange fees) and it seems that the exchange rate we have gotten in our currency (USD) vs the ARS in around 3-4% less with a credit card than the official rate.

Was curious if anyone if there is a reason for this & if taking out cash via WU or ATM (we have a debit card with no foreign fees that rebates ATM fees) would yield a higher rate consistently in Argentina than using a credit card?

When we did our initial research we saw that credit cards would possibly yield slightly higher than the official rate but that doesn't seem to be the case.

thanks in advance!