It sounds to me like John is asking you to enter into an agreement where you'll only be allowed to talk to John.
No, an impartial mediator is asking me to enter into an agreement where I can only talk to John or post in here (and a couple other private places).
I don't know details, but that sounds very unhealthy to me. I certainly wouldn't do that or ask that of anyone. And if someone asked it of me, I'd take it as a huge danger sign.
Trust me, John took it as such, and told her I would not be able to cope with that arrangement.
He's right.
Brenda