The question falls under the form of
I need advice on how to explain Cryptography in layman terms
Of which there is really only one truth about what cryptography is in all of IS:SE, and that is that it is a tool in the most basic of terms.
They needed help clarifying this which is a question opened up to some opinions about how the argument should be presented, but those are fine too since they aren't endorsement recommendations and aren't something actively harmful. They don't try to misinform what Cryptography is/n't, and really approach it more in a "Maybe if you present it this way it will help" sort of answer, of which there are many and are acceptable here since we offer advice since every situation isn't exact. Different explanations resonate differently with different groups, and so until he finds the right way to put it or we give him some information he was missing we might as well keep trying to help him find the right way to say it.