Ken G. = "Whoever designed your signature card is profoundly confused... ". Truly did make me LOL :-) . The authority to sign for a legal entity is still given & documented by a Corp. Resolution for example. And they are signing for the Corp as a Corp. Officer (most likely). So, as was said, this new rule is a separate issue / form.
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My opinions are just that, and might be worth what you paid for them.