In Season 7, Episode 7, Cersei asks the following
The crown accepts your truce... In return, the King of the north will extend this truce. He will remain in the north where he belongs. He will not take up arms against the Lannisters. He will not choose sides.
She says she asks because she knows Jon, Ned Starks son, will tell the truth. She is proven right about that.
I'm lost on why ask though. Why does she care if he stays in the north? Why is she concerned with him in particular? Did she expect he would accept and keep that promise? Was this request pointless either way because...
Cersei later reveals to Jamie that her plan was to play along with the truce and exploit it.
Why did Cersei make this request?