Read the part of the thread you’re responding to again. You’re misinterpreting it.
The initial question was: What if he told his wife, and his wife told his daughter? Then he didn’t break the confidentiality agreement (he only told his wife).
The response was: No, even though he was allowed to tell his wife, he would be required to tell her that she couldn’t tell anyone else, or it would break the confidentiality agreement.
The question isn’t whether you can tell someone you’re not allowed to tell if you make them promise not to tell. The question is whether telling someone you are allowed to tell gives them freedom to tell others. And the answer is no.