That isn't really an attempt at making people believe untrue things. I don't think it counts as puffery for that reason.
"In everyday language, puffery refers to exaggerated or false praise. Puffery serves to "puff up" what is being described. In law, puffery is usually invoked as a defense argument: it identifies futile speech, typically of a seller, which does not give rise to legal liability. In a circular manner, legal explanations for this normative position describe the non-enforceable speech as a statement that no "reasonable person" would take seriously anyway."
It seems puffery in both those senses.
Actual puffery comes about because there was a legitimate intent to deceive. As your (accurate) description of the law even implies: it's a defense for advertisers when they are caught being deceptive.