The insulators do use the foam board in the rim but they seal it in with some chaulking made just for that.
Our code calls for the exterior wall to be built 1" away from the concrete wall and that gap behind the wall at the top must be firestoped so fire in that wall can't get to the floor above. Depending on what you have for a sill on top of the concrete we intall either a 2x4 or a 2x6 against the sill and then the top plate of the wall goes against that and the space behind the wall is really close to that inch that is needed and the room comes up just as square as the room upstairs. The vapour barrier goes against the studs before the drywall. There are plastic shells to put switches and outlets in for vapour and the barrier is stuck to the floor with acustic sealer.
And the bottom plate does want something under it so it dosn't wick water up, plastic sheeting, sill gasket, tar paper.