I just did a bit of research and it looks as though "confidential" is specifically in regards to both parties being unable to use this conversation in court as evedince of anything unless they are making the argument the other party acted in bad faith (to me leaking the conversation to an outlet known to be biased against 1 of the parties seems like a bad faith action, but I'm no laywer or judge)

I know mediations which are more or less the same as this conversation was aren't even subject to discovery in court so the idea a laywer told whoever leaked this that it was A ok to do so is hard to wrap my brain around.