When someone offers you interest free money, you're doing it wrong if you're not taking advantage. If you're not using that money instead to pay off other interest bearing debt, then you are in fact, doing it wrong.
I don’t think what the person you quoted said was wrong, nor do I think what you said is wrong. Pay in full each month is generally the best advice, even if no interest. Before people know it they are paying $500/month, but hey it’s no interest.