S can tell you whatever they want. Same as I can and you can chose to believe it or not. Believe none of what they say 1/2 of what they do.
Also the boundaries are not for them. They are for you. The boundaries are for you to advertise to them. If S comes back to talk or whatever the boundaries are set in your life for you. Not to control them.
The person that you will spend the most time with in your life is yourself, so make yourself as interesting as possible.