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They were referring to cards issued as part of the Multibanco network. Unfortunately for tourists, there are many countries with their own independent card issuance authority, making it a hassle to pay with a Visa/Mastercard. Other examples include:
Credit card payment fees have now been capped in the EU, however merchants are known to be highly conservative and it's likely that Visa/Mastercard will take another decade to achieve full penetration in the EU. So for now, you'll have to sometimes use cash when visiting Portugal (or take your business elsewhere).